Acid Functionalized Graphene Quantum Research Articles

Construction of an advanced Co-doped V2O3 electrode material with significantly enhanced conductivity and structural stability for supercapacitors using asparagic acid-functionalized graphene quantum dot

Vanadium oxide become a promising electrode material for supercapacitors because of high capacitance and multiple redox. However, low intrinsic conductivity, narrow interlayer spacing and poor structural stability limit its practical...

Electrochemical detection of uric acid in human serum based on ultrasmall Ta2O5 nanoparticle anchored Pt atom with ultrahigh uricase and catalase activities.

The synthesis of ultrasmall Ta2O5 nanoparticle anchored Pt atom using aspartic acid-functionalized graphene quantum dot (Asp-GQD)is reported. The Asp-GQD was combined with tantalic acid and chloroplatinic acid to rapidly form water-soluble Ta-Asp-GQD and Pt-Asp-GQD complex. Followed by thermal annealing at 900 °C in N2 to obtain Ta2O5-Asp-GQD-Pt. The study shows that the introduction of Asp-GQD as a chelating agent and p-type semiconductor achieves to the formation of ultrasmall Ta2O5 nanoparticle, PN junction at the interface and Pt single atom anchored on the surface of Ta2O5 nanocrystals. The unique structure realizes ultrahigh uricase activity and catalase activities of Ta2O5-Asp-GQD-Pt. The Ta2O5-Asp-GQD-Pt was used as the bifunctional sensing material for the construction of an electrochemical uric acid sensor. The differential pulse voltammetric current at 0.45 V linearly increases with the increase of uric acid concentration in the range 0.001-5.00 mM with the detection limit of 0.41 μM (S/N = 3). The sensor exhibits a much better sensitivity compared with the reported methods for the detection of uric acid. The proposed analytical method has been applied tothe electrochemical detection of uric acid in human serum with a spiked recovery of 95-105%. The study also offers one way to design and synthesize multifunctional sensing materials with high catalytic activity.

The detection of the captured circulating tumor cells on the core-shell nanofibrous membrane using hyaluronic acid-functionalized graphene quantum dots.

In recent years, cancerous cases have increased remarkably worldwide, and metastasis is the leading cause of death. Therefore, research on the early detection of cancer and metastasis has expanded to aid successful cancer treatment. Here in this paper, at the first step, an electrospun nanofibrous membrane (NFM) with a core-shell structure was fabricated from PCL and HA to achieve cancer cell capturing (about 75% of cells). On the other hand, hyaluronic acid (HA)-functionalized graphene quantum dots (GQDs) were used to detect captured cancer cells on NFM through the changes in photoluminescence intensity. Therefore, CD44 receptor-HA interaction is the main principle used for both entrapment and detection of cancer cells. Results demonstrated the GQD-HA fluorescent intensity of solution decreased through the increase of the captured cancer cell numbers on NFM, which is related to the more adsorption of GQD nanocomposites to the CD44 receptors. In contrast, this intensity for noncancerous cells was steady with any cell concentrations. This difference shows the system's remarkable selectivity and specificity, which can be crucial in fluorescent imaging for accurate cancer diagnosis.

Glucosaminic acid-functionalized graphene quantum dots for sensitive detection of lactose in living cells and real food samples

The design of a nonenzyme sensor for lactose imaging in living cells is still a challenge nowadays. Enlightened by the saccharide–saccharide recognition at the cell surface, we prepared a graphene quantum dots–glucosaminic acid (GQDs–GA)-based fluorescent sensor for detection of lactose in living cells with high selectivity and sensitivity. GA acts as a receptor for lactose, while GQDs acts as a fluorescence signal transducer. Upon lactose addition, the fluorescence peaks at 315 and 429 nm were significantly enhanced owing to the blocking of photoinduced electron transfer. The interaction of the GQDs–GA sensor with lactose was mainly governed by the amide•••OH and OH•••π hydrogen bonding, supported by 1H NMR and density functional theory (DFT) calculations. A good linear relationship with the concentration of lactose was obtained over the range of 9.9 − 142.9 μM with a detection limit of 0.35 μM. The proposed sensor was used to detect lactose in real samples (tap water, milk, and honey) with a recovery range of 100.16–103.32%. More importantly, the GQDs–GA sensor can be used to track lactose in living cells. This work provides new insights into development of nonenzyme-based biosensor for single saccharide.

Bovine serum albumin-derived poly-l-glutamic acid-functionalized graphene quantum dots embedded UiO-66-NH2 MOFs as a fluorescence ‘On-Off-On’ magic gate for para-aminohippuric acid sensing

Evaluating para-aminohippuric acid (PAH) is emerging as a promising biomarker for the diagnostics of renal disease and other kidney-related illnesses. The present study aims to develop novel bovine serum albumin-derived poly-l-glutamic acid (PLGA) functionalized graphene quantum dots (PLGA-fGQDs) embedded in UiO-66-NH2 metal–organic frameworks (PLGA-fGQDs@UiO-66-NH2 MOFs) for monitoring of PAH. Initially, GQDs were achieved from bovine serum albumin (green precursor) via the single-step hydrothermal method. Here, functionalization with PLGA offers a tremendous increment in optical properties of GQDs. Then, highly luminescent UiO-66-NH2 MOFs were achieved using zirconium tetrachloride (ZrCl4) and 2-Aminoterephthalic acid (2-ATA) as a metal ion source and organic linker. Here, surface modification of GQDs with PLGA offered high quantum yield (QY), and responsiveness. Also, luminous UiO-66-NH2 MOFs afford a wide surface area for decorating of PLGA-fGQDs. The addition of gallium ions (Ga3+) into the probe solution resulted in fluorescence quenching (Turn-Off) whereas the incorporation of PAH resulted in fluorescence recovery (Turn-On). It is because of interaction with carboxylic functionality of PAH to Ga3+ followed by Ga-PAH complex formation. Herein, the wide concentration range and lowest limit of detection (LOD) were found to be 10 ng/mL to 900 ng/mL and 15.88 ng/mL, respectively. The specificity and real-time analysis in artificial urine validated the real-time adoption of a sensor for PAH detection. As well, it demonstrated good intraday/interday precision, stability analysis, and repeatability. In near future, the bundled illuminating PLGA-fGQDs@UiO-66-NH2 MOFs nanoprobe will be an attractive preference for tracking PAH in clinical specimens.

Folic acid-functionalized graphene quantum dots: Synthesis, characterization, radiolabeling with radium-223 and antiviral effect against Zika virus infection

The use of graphene quantum dots as biomedical devices and drug delivery systems has been increasing. The nano-platform of pure carbon has shown unique properties and is approved to be safe for human use. In this study, we successfully produced and characterized folic acid-functionalized graphene quantum dots (GQD-FA) to evaluate their antiviral activity against Zika virus (ZIKV) infection in vitro, and for radiolabeling with the alpha-particle emitting radionuclide radium-223. The in vitro results exhibited the low cytotoxicity of the nanoprobe GQD-FA in Vero E6 cells and the antiviral effect against replication of the ZIKV infection. In addition, our findings demonstrated that functionalization with folic acid doesn’t improve the antiviral effect of graphene quantum dots against ZIVK replication in vitro. On the other hand, the radiolabeled nanoprobe 223Ra@GQD-FA was also produced as confirmed by the Energy Dispersive X-Ray Spectroscopy analysis. 223Ra@GQD-FA might expand the application of alpha targeted therapy using radium-223 in folate receptor-overexpressing tumors.

Fabrication of poly (aspartic) acid functionalized graphene quantum dots based FRET sensor for selective and sensitive detection of MAGE-A11 antigen

In the present work, we investigated a label-free fluorescence resonance energy transfer (FRET) based poly (aspartic) acid (PAsP) functionalized graphene quantum dot (PAsP-GQDs) immunosensor for the selective and sensitive sensing of MAGE-A11 antigen.Synthesis of GQDs was accomplished with hydrothermal carbonization of Onion hull (ONI-GQDs). Synthesized PAsP-GQDs were characterized for fluorescence performance, functional compositions and morphological analysis. To form a typical FRET system, functionalized GQDs conjugated with anti-MAGE-A11 (antibody) using EDC/NHS chemistry served as an energy donor, while graphene nanosheets served as energy acceptors (quenchers). The fabricated PAsP-GQDs@M−A11−Ab immunosensor demonstrated high selectivity to MAGE-A11 with a broader detection range about of 0.05 ng mL−1 – 5 μg mL−1 (R2 = 0.9906) and a detection limit of about of 5.6 pg mL−1, with a rapid response time of 12 min. The performance of the developed immunosensor was established using real sample analysis, which showed an average recovery of 96.8 % with % RSD 0.71 indicating the high precision and reproducibility of the method. Furthermore, to implicate the post-functionalization modifications, cellular bioimaging potential and cytotoxicity studies were conducted as a comparative assessment. The present immunosensing strategies can be utilized as an analytical tool for detecting MAGE-A11 in various cancers.

Two-Dimensional Self-Assembly of Boric Acid-Functionalized Graphene Quantum Dots: Tunable and Superior Optical Properties for Efficient Eco-Friendly Luminescent Solar Concentrators.

Carbon-based nanomaterials hold promise for eco-friendly alternatives to heavy-metal-containing quantum dots (QDs) in optoelectronic applications. Here, boric acid-functionalized graphene quantum dots (B-GQDs) were prepared using bottom-up molecular fusion based on nitrated pyrenes and boric acid. Such B-GQDs with crystalline graphitic structures and hydrogen-bonding functionalities would be suitable model systems for unraveling the photoluminescence (PL) mechanism, while serving as versatile building blocks for supramolecular self-assembly. Unlike conventional GQDs with multiple emissive states, the B-GQDs exhibited excitation-wavelength-independent, vibronic-coupled excitonic emission. Interestingly, their PL spectra can be tuned without largely sacrificing the quantum yield (QY) due to two-dimensional self-assembly. In addition, such B-GQDs in a polystyrene matrix possessed an ultrahigh QY (∼90%) and large exciton binding energy (∼300 meV). Benefiting from broadband absorption, ultrahigh QY, and long-wavelength emission, efficient laminated luminescent solar concentrators (100 × 100 × 6.3 mm3) were fabricated, yielding a high power conversion efficiency (1.4%).

Electrochemical detection of omethoate and acetamiprid in vegetable and fruit with high sensitivity and selectivity based on pomegranate-like gold nanoparticle and double target-induced DNA cycle signal amplification

The study reports synthesis of gold-graphene quantum dot nanohybrid via reduction of chloroauric acid with arginine and aspartic acid-functionalized graphene quantum dot (Arg/Asp-GQD). The Arg/Asp-GQD-Au offers pomegranate-like architecture and Schottky heterojunction and was used for construction of electrochemical sensor for detection of omethoate and acetamiprid coupled with double target-induced DNA cycles. Target molecule hybridizes with aptamer DNA in duplex DNA to release auxiliary strand DNA. This triggers the DNA cycle and brings one redox probe to electrode surface. By the DNA cycle, one target molecule can transfer many redox probes to electrode surface and produces a significant signal amplification. The detection signal was enhanced by catalysis of Arg/Asp-GQD-Au toward redox of these probes due to its excellent catalytic activity. Differential pulse voltammetric peak current linearly increases with increasing target concentration between 5 × 10−14 and 5 × 10−10 M with detection limit of 1.67 × 10−14 Μ (S/N = 3) for omethoate and between 1 × 10−14 and 5 × 10−10 M with detection limit of 3.33 × 10−15 M (S/N = 3) for acetamiprid. The proposed method provides a much better sensitivity and selectivity and was successfully applied to detection of omethoate and acetamiprid in vegetable and fruit.

Highly Sensitive and Selective Electrochemical Aptasensor with Gold-Aspartic Acid, Glycine Acid-Functionalized and Boron-Doped Graphene Quantum Dot Nanohybrid for Detection of Α-Amanitin in Blood

Highly Sensitive and Selective Electrochemical Aptasensor with Gold-Aspartic Acid, Glycine Acid-Functionalized and Boron-Doped Graphene Quantum Dot Nanohybrid for Detection of Α-Amanitin in Blood

Fabrication of Poly (Aspartic) Acid Functionalized Graphene Quantum Dots Based FRET Sensor for Selective and Sensitive Detection of MAGE-A11 Antigen

Fabrication of Poly (Aspartic) Acid Functionalized Graphene Quantum Dots Based FRET Sensor for Selective and Sensitive Detection of MAGE-A11 Antigen

A Facile Co-Deposition Approach to Construct Functionalized Graphene Quantum Dots Self-Cleaning Nanofiltration Membranes

In this study, a novel photocatalytic self-cleaning nanofiltration (NF) membrane was fabricated by constructing aspartic acid-functionalized graphene quantum dots (AGQDs) into the polydopamine/polyethyleneimine (PDA/PEI) selective layer via the co-deposition method. The chemical composition, microstructure, and hydrophilicity of the prepared membranes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA). Meanwhile, the effects of PEI molecular weight and AGQDs concentration on NF membrane structures and separation performance were systematically investigated. The photocatalytic self-cleaning performance of the PDA/PEI/AGQDs membrane was evaluated in terms of flux recovery rate. For constructing high-performance NF membranes, it is found that the optimal molecular weight of PEI is 10,000 Da, and the optimal concentration of AGQDs is 2000 ppm. The introduction of hydrophilic AGQDs formed a more hydrophilic and dense selective layer during the co-deposition process. Compared with the PDA/PEI membrane, the engineered PDA/PEI/AGQDs NF membrane has enhanced water flux (55.5 LMH·bar−1) and higher rejection (99.7 ± 0.3% for MB). In addition, the PDA/PEI/AGQDs membrane exhibits better photocatalytic self-cleaning performance over the PDA/PEI membrane (83% vs. 69%). Therefore, this study provides a facile approach to construct a self-cleaning NF membrane.

Structure-performance relationships between amino acid-functionalized graphene quantum dots and self-cleaning nanofiltration membranes

To develop self-cleaning nanofiltration (NF) membranes with excellent desalination performance, five kinds of amino acid-functionalized graphene quantum dots (AA-fGQDs) were synthesized and introduced into the active layers of the thin-film nanocomposite (TFN) membranes via the interfacial polymerization (IP) method. The synthesized AA-fGQDs and the resulting TFN NF membranes were systematically characterized to investigate the structure-performance relationships between the AA-fGQDs and the NF membranes. The results showed that the desalination and photocatalytic self-cleaning performance of the fabricated TFN membranes were closely related to the types and structures of AA-fGQDs. The TFN membranes incorporating AA-fGQDs with the polar amino acids exhibit better desalination performance than those incorporating AA-fGQDs with the non-polar amino acids, overcoming the trade-off effect between water flux and salt rejection. The TFN-Asp-GQDs membrane exhibits superior water permeability of 27.35 LMH·bar−1 while maintaining high salt rejection (97.95% for Na2SO4), equal to 4.41 times of the TFC-blank membrane (6.20 LMH·bar−1) and 1.85 times of the TFN-GQDs membrane (14.78 LMH·bar−1). Moreover, the TFN membranes incorporating AA-fGQDs with low bandgap energies exhibit better self-cleaning performance than those incorporating AA-fGQDs with high bandgap energies. The TFN-Cys-GQDs membrane shows the best self-cleaning performance with the highest water flux recovery (96.95%), mainly ascribed to the low bandgap energy of Cys-GQDs. Therefore, the desalination and self-cleaning performance of NF membranes can be effectively regulated by the types of AA-fGQDs. It also suggests that the utilization of suitable AA-fGQDs presents a novel and promising strategy to develop self-cleaning NF membranes with excellent desalination performance.

Do amino acid functionalization stratagems on carbonaceous quantum dots imply multiple applications? A comprehensive review.

Amino acids are the noteworthy entity among biological molecules with diverse properties such as zwitterionic and amphoteric. Functionalizing carbon-based quantum dots using amino acids might be used for the extreme enhancement of electronic and optical properties of quantum dots and improve the performance of the resultant amino acid-functionalized quantum dots. The amino acid-functionalized quantum dots are highly soluble, sustainable, and biocompatible with virtuous optical and electrical performance, which makes them potential and suitable candidates for fabricating optoelectronic devices. The tenacity of using amino acids as functional groups to functionalize quantum dots and their novel properties are conferred to attain their multiple applications. The goal of this review is to provide the choices of amino acids based on the desired applications and a variety of functionalization techniques to make them a noteworthy material for future applications. The method of one-step and two-step functionalization strategies along with the properties of the resultant functionalized quantum dots and their plausible applications and future scope of the material are highlighted. Amidation is the basic principle behind the functionalization of quantum dots with amino acids. This review would be an exciting prospect to explore the pathways of the possible applications in different domains, in which the amino acid-functionalized quantum dots have not yet been explored. Further, this review article helps in pitching a variety of prominent applications right from sensors to energy storage systems either using the optical property or electronic property of amino acid-functionalized quantum dots.

Thin-film nanocomposite nanofiltration membrane with enhanced desalination and antifouling performance via incorporating L-aspartic acid functionalized graphene quantum dots

To fabricate thin-film nanocomposite (TFN) nanofiltration (NF) membrane with enhanced desalination and antifouling performance, L-aspartic acid functionalized graphene quantum dots (AGQDs), integrating the advantages of L-aspartic acid and graphene quantum dots (GQDs), were successfully synthesized and incorporated into the polyamide (PA) selective layer via interfacial polymerization (IP) method. The fabricated TFN membranes with various AGQDs contents were systematically characterized by the microstructures, surface properties, desalination, and antifouling performance. The optimal AGQDs concentration in the aqueous solution reaches 3000 ppm, the resultant TFN-3 membrane exhibits an outstanding water permeance of 18.5 LMH/bar, 60.9% higher than the TFC-blank membrane. Meanwhile, the TFN-3 membrane possesses a higher Na2SO4 rejection than that of the TFC-blank membrane (98.4% vs 95.7%). Additionally, the TFN-3 membrane shows superior antifouling performance over the TFC-blank membrane in the presence of either the negatively charged foulant (BSA) or the positively charged foulant (lysozyme). An appropriate amount of AGQDs added into aqueous solution favors the formation of a smooth, thin, hydrophilic, and electrically neutral selective layer. As a result, the overall separation performance of the TFN-3 membrane, especially the desalination and antifouling performance, are significantly enhanced with the help of AGQDs. Therefore, the incorporation of amino acid-functionalized GQDs into the PA selective layer presents a novel strategy to produce a high-performance NF membrane for water desalination.

Synthesis and Characterization of 2-Aminoethylphosphonic Acid-Functionalized Graphene Quantum Dots: Biological Activity, Antioxidant Activity and Cell Viability

A facile, environmentally friendly one-step reaction for the preparation of luminescent N-doped graphene quantum dots (GQDs) involving a hydrothermal reaction between citric acid and 2-aminoethylphosphonic acid was designed. Graphene quantum dots were characterized by UV-Vis, FT-IR spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and dynamic light scattering (DLS). Furthermore, the biological activity of the GQDs was studied. UV-Vis spectroscopy studies of the interactions between the GQDs and calf thymus DNA (CT-DNA) showed that the compound interacts with CT-DNA via intercalative binding. DNA cleavage study showed that the GQDs cleaved DNA oxidatively. In addition, antioxidant activity of N-doped GQDs was measured using the DPPH method. As the concentration of the compound increased, the antioxidant activity also increased. According to cell viability analyses results, the N-doped GQDs showed cell viability (70 %) when the concentration reached 228 μg/mL for A549, 200 μg/mL for MDA-MB-231 and 140 μg/mL for NIH-3T3 cell lines with 24 h incubation.

Correction to Exceptionally High Payload of the IR780 Iodide on Folic Acid-Functionalized Graphene Quantum Dots for Targeted Photothermal Therapy.

Correction to Exceptionally High Payload of the IR780 Iodide on Folic Acid-Functionalized Graphene Quantum Dots for Targeted Photothermal Therapy.

Electrochemical detection of cancer cells in human blood using folic acid and glutamic acid-functionalized graphene quantum dot-palladium@gold as redox probe with excellent electrocatalytic activity and target recognition

Determination of circulating cancer cells in human blood is potential to be convenient diagnosis of different cancers. The study reports one strategy for synthesis of folic acid and glutamic acid-functionalized graphene quantum dot-palladium@gold (FA/Glu-GQD-Pd@Au). Firstly, FA/Glu-GQD was prepared by thermolysis of the mixture of citric acid, glutamic acid and folic acid. Then, it was used as the stabilizer and reducer for synthesis of FA/Glu-GQD-Pd@Au. The resulting hybrid was employed as one redox probe for construction of electrochemical sensing platform for cancer cells. The study reveals that the FA/Glu-GQD-Pd@Au offers one core@shell nanostructure. Pd nanocube as the core was covered by gold nanocrystal as the shell. For the detection, Pd@Au gives high electrocatalytic activity due to its unique structure as well as combination with FA/Glu-GQD. FA/Glu-GQD strongly binds with cancer cells to produce target recognition. FA/Glu-GQD occurs reversible redox reactions on the electrode surface and produces electrochemical signal for binding cancer cells. Pd@Au in situ catalyzes redox of FA/Glu-GQD and achieves to significant signal amplification. The sensor based on FA/Glu-GQD-Pd@Au exhibits ultrahigh sensitivity for detection of cancer cells. The differential pulse voltammetric peak current linearly reduces with the increase of cancer cells in the range of 3−1 × 105 HepG2 cells mL−1 with the detection limit of 2 cells mL−1 (S/N = 3). The proposed analytical method has been successfully applied in electrochemical detection of circulating cancer cells in human blood.

Functionalized Graphene Quantum Dot Interfaced Electrochemical Detection of Cardiac Troponin I: An Antibody Free Approach

According to the World Health Organization (WHO), cardiovascular disease (CVD) is the leading cause of death in the world every year. The design and development of biosensors for the detection of CVD markers could be one of the major contributions of the scientific community to society. In this context, acetic acid functionalized graphene quantum dots (fGQDs) were used as an interface for the electrochemical detection of cardiac Troponin I (cTnI). The interaction of cTnI with fGQDs for the early diagnosis of acute myocardial infarction was investigated using cyclic voltammetry (CV) and amperometry. The carbodiimide conjugation between the N-H group of cTnI and the functionalized COOH group on GQDs enabled the detection of cTnI biomarker. The same sensing mechanism was confirmed using Fourier Transform Infrared Spectrometry (FTIR). The fGQDs modified Au electrode showed remarkable electrocatalytic oxidation of cTnI with good stability and sensitivity over a linear range of 0.17 to 3 ng mL−1 and a low detection limit of 0.02 ng mL−1. Bland-Altman plots substantiate a bias between the intra-/inter-cTnI assay and calibrated cTnI assay with 95% limits of agreement (mean difference ± 1.96 SD). The aim of this study is to describe an innovative method to detect cardiac biomarker cTnI and provide preliminary data on its diagnostic capacity. At the same time, its applicability in clinical setting will have to be validated with a significant number of samples collected from patients.

Electrochemical aptasensor for detection of acetamiprid in vegetables with graphene aerogel-glutamic acid functionalized graphene quantum dot/gold nanostars as redox probe with catalyst

Glutamic acid-functionalized graphene quantum dots (Glu-GQD) was prepared by pyrolysis of citric acid and glutamic acid and used as reducing agent and stabilizer to produce Glu-GQD/Au in the presence of tannic acid. The resulting Glu-GQD/Au was covalently connected with aptamer (Apt) of acetamiprid to obtain one redox probe with catalyst. The study shows that Glu-GQD/Au offers nanostar-like structure with average particle size of 102.5 nm, composing of several nanometer-sized gold nanocrystals with the rich of sharp edges and corners. The unique structure makes gold nanostars good electrocatalytic activity, which was further improved by combination with Glu-GQD. In the redox probe, Glu-GQD can carry out reversible redox reaction on the electrode surface due to its high electroactivity. Gold nanostars in-situ catalyzes redox reactions of Glu-GQD and leads to an improved electrochemical behavior. Aptamer can specifically bind with acetamiprid and produce sensitive and selective electrochemical response. The electrochemical aptasensor based on Glu-GQD/Au-Apt/graphene aerogel exhibits ultrahigh sensitivity and selectivity for detection of acetamiprid. The differential pulse voltammetric signal linearly decreases with increasing acetamiprid concentration in the range from 1.0 fM to 1 × 105 fM with detection limit of 0.37 fM (S/N = 3). The aptasensor has been successfully applied in electrochemical detection of acetamiprid in vegetables.