Amino-functionalized Graphene Research Articles

Amino-functionalized graphene quantum dots as a photoluminescent probe for in vitro cellular imaging of human lung cancer cell lines

Graphene-based fluorescent materials, particularly graphene quantum dots (GQDs), have emerged as a new class of biomedical agents. In the present study, functionalised GQDs have a better chance of being employed in a broader range of bioapplications because of their proven low toxicity, outstanding biocompatibility, and enhanced fluorescence properties. For this purpose, amino-functionalised GQDs (AF-GQDs) were synthesised via hydrothermal treatment by treating graphene oxide in ammonia with heat and water. The as-prepared AF-GQDs samples were characterised using a variety of techniques, including x-ray diffraction analysis (XRD), high-resolution transmission electron microscopy (HR-TEM), and photoluminescence (PL) spectroscopy. The results show that AF-GQDs are merely hexagonal, with an average size of about 8 nm. Also, AF-GQDs are highly soluble in water and display excellent luminescence behaviour. After 48 h of incubation, the MTT results showed that more than 63% of the cells were still alive, even at high concentrations (500 g ml−1) of AF-GQDs. In addition, the AO/EB staining results also showed that the AF-GQDs had the most robust green fluorescence (viable cells). This makes them a promising agent for biomedical imaging because they have good optical properties, are readily soluble in water, are biocompatible, and are not toxic.

Amino-functionalized graphene oxide affects bacteria–phage interactions in aquatic environments

Amino-functionalized graphene oxide affects bacteria–phage interactions in aquatic environments

Controllable functionalization of amino-functionalized graphene quantum dots as fluorescent probe for detection of Cu(Ⅱ) ions detection

Herein, the amino-functionalized graphene quantum dots (GQDs) can be applied for selective detection of Cu(Ⅱ) ions in solutions via photoluminescence (PL) measurement, the PL emission intensities of the GQDs gradually decreased with the increase of Cu2+ concentration (0–100 μm), the PL intensity (quenching effect) decreases almost linearly with increasing Cu2+ concentration. Its correlation coefficient R2 is 0.9529. Quenching of the PL emission by the presence of copper(Ⅱ) ions is attributed to the surface functional groups attached to the GQDs, which can interact with metal ions so that the electrons in the excited state of the GQDs are transferred into the unoccupied orbits of Cu(Ⅱ) ions. Corresponding physical mechanism is proposed to gain an understanding about how the presence of the Copper(Ⅱ) ions can affect the PL emission from GQDs.

Amino-Modified Graphene Oxide from Kish Graphite for Enhancing Corrosion Resistance of Waterborne Epoxy Coatings.

Waterborne epoxy (WEP) coatings with enhanced corrosion resistance were prepared using graphene oxide (GO) that was obtained from kish graphite, and amino-functionalized graphene oxide (AGO) was modified by 2-aminomalonamide. The structural characteristics of the GO and AGO were analyzed using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). And the anti-corrosive performance of waterborne epoxy-cased composite coatings with different addition amounts of AGO was investigated using electrochemical measurements, pull-off adhesion tests, and salt spray tests. The results indicate that AGO15/WEP with 0.15 wt.% of AGO has the best anti-corrosive performance, and the lowest frequency impedance modulus increased from 1.03 × 108 to 1.63 × 1010 ohm·cm-2 compared to that of WEP. Furthermore, AGO15/WEP also demonstrates the minimal corrosion products or bubbles in the salt spray test for 200 h, affirming its exceptional long-term corrosion protection capability.

Diethylenetriamine-functionalized reduced graphene oxide having more amino groups for methylene blue removal.

To obtain a high-performance amino-functionalized graphene, a new aminated graphene was prepared through a substitution reaction between chlorine-functionalized reduced graphene oxide and diethylenetriamine. The product exhibits high nitrogen content uniformly distributed in its sheets, with diethylenetriamine covalently attached to these sheets. The C-N bond in the product was certified by the Fourier transform infrared spectrum, which implies the successful attachment of diethylenetriamine to the graphene sheets. The average interlayer spacing is 0.42 nm. Diethylenetriamine features many more amino groups that act as ligands and spacers during adsorption and layer stacking processes. Compared with the adsorption capacities of reduced graphene oxide (77.1 mg g-1) and activated carbon (46.7 mg g-1), the product exhibits higher adsorption capacity (291.4 mg g-1). The adsorption process fits the quasi-first-order model and Langmuir model. Physical adsorption plays a primary role in the adsorption process. The amino group of the product easily reacts with other chemicals, making it a useful intermediate for other graphene materials.

Rheology of amino-functionalized graphene oxide suspensions in hydrogels

Rheology of amino-functionalized graphene oxide suspensions in hydrogels

Improved corrosion protection performance of electrophoretic epoxy coatings with the incorporation of amino-functionalized graphene oxide

Improved corrosion protection performance of electrophoretic epoxy coatings with the incorporation of amino-functionalized graphene oxide

Cascade selective recognition of H2O2 and ascorbic acid in living cells using carbon-based nanozymes with peroxidase-like activity

The design of optical nanosensors based on carbon nanozymes has gained considerable interest in analyte detection. In this study, a simple and rapid fluorescence/colorimetry probe, NH2GQDs/o-phenylenediamine (OPD), was constructed by combining amino-functionalized graphene quantum dots (NH2GQDs) and o-phenylenediamine. In the presence of NH2GQDs/H2O2, OPD was oxidized to 2,3-diaminophenazine (DAP), giving fluorescent and colorimetric signals, which can be used to quantitatively measure H2O2. Furthermore, NH2GQDs/OPD/ H2O2 exhibited high selectivity and sensitivity for detecting ascorbic acid (AA) with a detection limit of 0.062 μM using the fluorescent method. Its selectivity for AA was ascribed to the formation of the condensation compound of DAP with dehydroascorbic acid rather than the quinoxaline path for dopamine and glucose. The colorimetric sensing system NH2GQDs/OPD displayed yellow in the presence of H2O2, while it changed to green upon adding AA. This sensing system was successfully applied for imaging H2O2 and AA in human cervical cancer cells and onion tissues. Additionally, the flexible sensing system can be used to fabricate the logic gate “AND.” The results provide a valuable method for its potential application in the biosensing, clinical medicine, and food industries.

Cellulose circular economy: Amino-functionalized graphene quantum dots as highly sensitive vaccine indicators

Cellulose is a highly content natural polymer that can be extracted from plants. Rice straw is a valuable resource because it is rich in cellulose. This study aims to develop a technology to extract and utilize cellulose from rice straw, which would otherwise be discarded. Cellulose derived from rice straw is used to synthesize low-biotoxicity, high-performance graphene quantum dots. Cellulose is hydrolyzed into glucose and processed into graphene quantum dots using the hydrothermal method, which is a green synthetic route. The 3-(4,5-dimethylthiazol-2-yl)− 2,5-diphenyltetrazolium bromide assay shows that the natural biomass (cellulose)-derived graphene quantum dots have low biological toxicity and cell viability that exceeds 100% (48 h, 400 micrograms per milliliter). Their luminescence properties, chemical stability, and biological toxicity are significantly improved by subsequent reduction and amination. Subsequently, amino-functionalized graphene quantum dots are used as a display agent for vaccine detection, which quantified secondary antibody concentration with a detection limit of 2 pg/mL, excellent linearity (r2 = 0.9982), and a low coefficient of variation of < 0.04%, outperforming the existing 3,3′5,5′-tetramethylbenzidine. This study demonstrates that graphene quantum dots synthesized from natural polymers are suitable for low-toxicity applications, such as vaccine indicators.

Mild preparation of amino-functionalized graphene oxide-based recyclable aerogel to efficiently adsorb methyl orange

Mild preparation of amino-functionalized graphene oxide-based recyclable aerogel to efficiently adsorb methyl orange

Thin film nanocomposite polyamide membrane doped with amino-functionalized graphene quantum dots for organic solvent nanofiltration

Thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane with improved separation performance was fabricated via interfacial polymerization reaction between amine-functionalized graphene quantum dots (af-GQDs) doped aqueous monomer solution of m-phenylenediamine (MPD) and n-hexane solution containing trimesoyl chloride (TMC) monomer. We emphasize the employment of extra-low content for both af-GQDs and MPD, so that we could maximize the function of these nanomaterials and eliminate their aggregation at the same time. The af-GQDs nanomaterials could regulate the interfacial polymerization process and could be strongly anchored in the polyamide film via covalent bonding, hence could prevent their loss while providing more channels for faster solvent penetration. As a result, the optimized OSN membrane, TFN-50, shows a super-smooth surface, with a surface roughness as low as 4.3 ± 0.2 nm, and excellent pure solvent permeances which reach 135.8, 112.7, and 69.8 L m−2 h−1 MPa−1 for methanol, DMF and ethanol, respectively, as well as a very high Rhodamine B (RDB, 479 Da) rejection of up to 99.2%, and an ethanol permeance of 61.4 L m−2 h−1 MPa−1. Furthermore, the TFN-50 OSN membrane still shows excellent filtration performance after being submerged in DMF for 336 h or continuous crossflow filtration with Rose bengal (RB, 1017 Da)/DMF solution for 136 h, demonstrating its excellent solvent resistance.

Antifouling and Chemical-Resistant Nanofiltration Membrane Modulated by a Functionalized MWCNT Interlayer for Efficient Dye/Salt Separation at High Salinity.

Dye/salt separation in textile wastewater is of great importance. Membrane filtration technology is an environmentally friendly and effective approach to solve this issue. In this study, a thin-film composite membrane with a tannic acid (TA)-modified carboxylic multiwalled carbon nanotube (MWCNT) interlayer (M-TA) was prepared by interfacial polymerization with amino-functionalized graphene quantum dots (NGQDs) acting as aqueous monomers. The addition of the M-TA interlayer favored the formation of a thinner, more hydrophilic, and smoother selective skin layer for the composite membrane. The pure water permeability of the M-TA-NGQDs membrane was ∼9.32 L m-2 h-1 bar-1, which was higher than that of the NGQDs membrane without the interlayer. Meanwhile, the M-TA-NGQDs membrane presented better methyl orange (MO) rejection (97.79%) than the NGQDs membrane (87.51%). The optimal M-TA-NGQDs membrane exhibited excellent dye rejection (Congo red (CR): 99.61%; brilliant green (BG): 96.04%) and low salt rejection (NaCl < 15%). Noticeably, the M-TA-NGQDs membrane displayed effective selective separation performance (CR and BG > 99%) for dye/NaCl mixed solutions even at a high NaCl concentration of 50,000 mg/L. Furthermore, the M-TA-NGQDs membrane presented high water permeability recovery ratio values (91.02-98.20%). Importantly, the M-TA-NGQDs membrane showed excellent chemical stability (acid/alkali resistance). Generally, the fabricated M-TA-NGQDs membrane exhibited a great prospect for applications in dye wastewater treatment and water recycling, especially for the effective selective separation of dye/salt mixtures for high-salinity textile dyeing wastewater.

High-damping polyurethane-based composites modified with amino-functionalized graphene

A series of damping composites containing polyurethane/poly (butyl methacrylate) (PU/PBMA) as the polymer matrix and graphene nanoplates (GNP) or amino-functionalized graphene nanoplates (NGNP) as a modifier was successfully synthesized through in situ polymerization. The chemical structure, microphase configuration, damping properties, and thermal stability of the GNP–PU/PBMA and NGNP–PU/PBMA composites were evaluated. Fourier-transform infrared and X-ray photoelectron spectroscopic studies revealed that the amino (–NH2) groups on the NGNP surface presumably reacted with the isocyanate (R–N = C = O) groups of the polymer matrix. This led to robust bonding between the NGNP and the hard segments in PU, resulting in an NGNP/polymer-matrix compatibility superior to that of GNP–PU/PBMA. Structural investigations based on scanning electron microscopy and atomic force microscopy revealed dispersion-state-related differences between the GNP and NGNP in the PU/PBMA matrix; the amino-functionalized GNP were more uniformly dispersed in the polymer matrix than their unmodified counterparts, and microphase separation between the hard and soft segments intensified in NGNP–PU/PBMA, resulting in a greater degree of phase separation, as confirmed by small-angle X-ray scattering analysis. Dynamic mechanical analysis (DMA) revealed that the maximum damping peak (tan δmax) of the composite with 0.7 wt.% NGNP was 22.7% higher than that of pristine PU/PBMA. Additionally, a large independent damping peak appeared in the DMA curve of 0.7 wt.% NGNP–PU/PBMA in the high-temperature range, indicating broadening of the damping temperature range. Moreover, the NGNP incorporation effectively improved the thermal stability of the composite. Overall, this study demonstrates the viability of realizing PU-based materials with excellent thermodynamic and damping properties by incorporating amino-bearing NGNP.

Thiol-End-Group Dendrons Decorated with Gold Nanoparticles Immobilized on Amino-Functionalized Graphene Oxide for SERS Detection

Surface-enhanced Raman scattering (SERS) has abundant chemical fingerprint information to analyze complex analytes under aqueous conditions. However, SERS requires uniform metal particles to generate a hotspot effect and improve sensitivity and enhancement by localized surface plasmon resonance. Therefore, in this study, SERS detection chips have been developed using uniform gold nanoparticle (AuNP) arrays embedded on thiol-end-group dendritic polymers immobilized on amino-functionalized graphene oxide (AGO) thin films of transmission electron microscopy (TEM) grids. The graphene oxide (GO) thin film was fabricated by low-damage plasma with mixed gas (O2/H2) and then further functionalized by diethylenetriamine to form AGO substrates. Based on the efficient building block of dual-functional 4-isocyanato-4′-(3,3-dimethyl-2,4-dioxo-azetidino)-diphenylmethane (IDD), the 0.5 and 1.5 generations of thiol-end-functionalized poly(urea/malonamide) dendrons (DG0.5-SH and DG1.5-SH) were precisely synthesized and grafted onto AGO substrates. The interparticle gap of AuNPs could be well controlled and decorated on these thiol-end-group dendrons to achieve the optimal SERS enhancement effect by manipulating the sizes of AuNPs and generating dendrons. The results indicate that 31 nm AuNPs immobilized on the DG0.5-SH@AGO substrate exhibited reproducible and strong SERS enhancement compared with free AuNPs. Graphene-based SERS substrates provide rapid and stable SERS detection in solutions, which offers great potential for practical applications in detecting biomolecules and environmental pollutants.

Fabrication of Flexible Poly(m-aminophenol)/Vanadium Pentoxide/Graphene Ternary Nanocomposite Film as a Positive Electrode for Solid-State Asymmetric Supercapacitors.

In this study, poly(m-aminophenol) (PmAP) has been investigated as a multi-functional conductive supercapacitor binder to replace the conventional non-conductive binder, namely, poly(vinylene difluoride) (PVDF). The kye benefits of using PmAP are that it is easily soluble in common organic solvent and has good film-forming properties, and also its chemical functionalities can be involved in pseudocapacitive reactions to boost the capacitance performance of the electrode. A new ternary nanocomposite film based on vanadium pentoxide (V2O5), amino-functionalized graphene (amino-FG) and PmAP was fabricated via hydrothermal growth of V2O5 nanoparticles on graphene surfaces and then blending with PmAP/DMSO and solution casting. The electrochemical performances of V2O5/amino-FG/PmAP nanocomposite were evaluated in two different electrolytes, such as KCl and Li2SO4, and compared with those of V2O5/amino-FG nanocomposite with PVDF binder. The cyclic voltametric (CV) results of the V2O5/amino-FG/PmAP nanocomposite exhibited strong pseudocapacitive responses from the V2O5 and PmAP phases, while the faradaic redox reactions on the V2O5/amino-FG/PVDF electrode were suppressed by the inferior conductivity of the PVDF. The V2O5/amino-FG/PmAP electrode delivered a 5-fold greater specific capacitance than the V2O5/amino-FG/PVDF electrode. Solid-state asymmetric supercapacitors (ASCs) were assembled with V2O5/amino-FG/PmAP film as a positive electrode, and their electrochemical properties were examined in both KCl and Li2SO4 electrolytes. Although the KCl electrolyte-based ASC has greater specific capacitance, the Li2SO4 electrolyte-based ASC delivers a higher energy density of 51.6 Wh/kg and superior cycling stability.

Amino-functionalization-assisted construction of CoP/N, P co-doped graphene to enhance stable lithium storage via electrostatic interaction and strong bonds

Compounding CoP nanoparticles with graphene can serve as promising anode materials for high-performance lithium-ion batteries. However, the weak binding and dispersion between CoP and graphene usually lead to poor structural stability limiting the lithium storage performance. Herein, an amino-functionalization-assisted one pot self-assembly method is employed to synthesize CoP/nitrogen, phosphorus co-doped graphene composites (CoP/NPG) with a highly stable 3D porous structure. The negatively charged phytic acid can act as a bridging connection between the positively charged amino-functionalized graphene and Co2+ by strong electrostatic attraction, ensuring the synthesized CoP nanoparticles are uniformly distributed on NPG sheets with high conductivity and plenty of active centers. Meanwhile, establishing strong C–P and Co–O–C surface chemical bonds between CoP and NPG improves the structural strength and promotes fast electron/ion transport, which effectively alleviates the volume expansion of CoP. Benefiting from these advantages, the CoP/NPG electrode displays high lithium storage capacity (917.9 mAh g − 1 at 0.5 A g − 1 after 600 cycles), ultra-long cyclic stability (434.8 and 350.5 mAh g − 1 at 3.0 and 5.0 A g − 1 after 3000 cycles) and fast pseudocapacitive charge storage (contribution even up to 97% at 2.0 mV s − 1). This strategy offers promising prospects for the preparation of highly stable anode materials.

Preparation and Anticorrosive Performance of Waterborne Epoxy Resin Composite Coating with Amino-Modified Graphene Oxide

A waterborne epoxy coating with superior corrosion resistance was developed by using a novel amino-functionalized graphene oxide (GO) that was modified by 2,5-diaminobenzenesulfonic acid. A battery of characterization methods, such as Fourier transform infrared spectroscopy (FT-IR), Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), was used to prove that DGO was successfully prepared by grafting the amino of 2,5-diaminobenzenesulfonic on GO. The results indicated that the surface of DGO became rougher than GO, but a complete sheet structure was still maintained after modification; the optimal modified GO could be achieved when the mass ratio of 2,5-diaminobenzenesulfonic acid and GO was 5:1. The electrochemical impedance spectroscopy (EIS) tests indicated that the impedance at 0.01 Hz of a coating with 0.2 wt.% DGO still remained at a relatively high value after immersion for 48 h in 3.5 wt.% NaCl, which was about one order higher than a pure waterborne epoxy resin coating, and the corrosion current density decreased from 3.76 × 10-11 A/cm2 to 3.62 × 10-12 A/cm2. The dry adhesion and wet adhesion increased to 1.90 and 1.22 MPa, respectively, and the adhesion loss decreased from 53% to 36%. These interesting features could make waterborne epoxy coatings a promising anticorrosion coating for metal in long-term protection.

The synergistic antioxidant effect of polydopamine coating with amino-functionalized graphene quantum dots on osteoblast protection against oxidative stress

Oxidative stress is a major pathological feature in patients with metabolic bone diseases and isn’t conducive to postoperative osseointegration of implants. Although the free-radical scavenging activities of polydopamine (PDA) have been reported, its antioxidant-active catechol structure is susceptible to oxidation. Here, amino-functionalized graphene quantum dots (GQDs) were introduced into PDA to protect catechol structure from oxidation and expand its free-radical scavenging capacity. Compared to the clinically used hydroxyapatite (HAp) coating and the PDA-HAp coating, the GQD/PDA-HAp coating exhibited higher capacity to scavenge ABTS·+, DPPH and O2·-. The enhanced antioxidant effect of the GQD/PDA-HAp coating was ascribed to the combined effects of the sp2-hybridized carbon in GQDs and more catechol groups in PDA, indicating the synergistic antioxidant relationship between GQDs and PDA. In addition, the amino-functionalized GQDs increased the catechol content and the reducibility of the GQD/PDA coating as confirmed by Folin-Ciocalteu colorimetric assay and mediated electrochemical probing. In vitro studies showed that the GQD/PDA-HAp coating minimized intracellular reactive oxygen species production and protected osteoblast viability against H2O2-induced oxidative stress. Taken together, introducing amino groups in PDA is an efficient approach to preserve its structural related antioxidant properties which may broaden its application in treating oxidative stress-related diseases.

Amino-functionalized graphene oxide membranes for efficient separation of Sr2+ ions

Graphene oxide (GO) membranes were integrated with diverse nitrogen functional groups by subjecting to ammonia (NH3) vapours and evaluated for resultant changes in their chemical functioning and strontium (Sr) adsorption performance. Exposure to NH3 vapours amends the functional groups of GO, introduces amine, amide, ammonium functionalities and generates abundant sites prone to react with Sr2+ ions. The extent of GO restructuring and repercussions on Sr adsorption behaviour were examined using different GO precursors, NH3 treatment methods, membranes with varying GO mass and other nitrogen reagents namely, tri-isooctyl amine, pyridine, N,N-dimethyl acetamide. Nitrogen group functionalization enhances the Sr adsorption capacity of GO membranes nearly by two times, irrespective of the NH3 exposure duration and nature of precursor GO membranes. These NH3 subjected GO membranes displayed optimum Sr adsorption performance of ~475 mg/g, reusable at least for nine filtration cycles and importantly, capable of discharging 35–60 % of adsorbed Sr. The N-group supported Sr separation demonstrated in the present work is an energy efficient solid state membrane based procedure, which also lays a road map for development of amine, amide, ammonium functionalized GO layers and provides flexible platform for separation of all those toxic elements displaying affinity to complex with N-groups.

YAP/TFRC/ALOXE3 signaling is involved in ferroptosis and neuroinflammation triggered by amino-functionalized graphene quantum dots

Recently, graphene quantum dots (GQDs) have been attracting extensive interests in a widespread application, but the little information on the risk assessments of GQDs could impose a restriction on their contributions in the neuroscience. In this study, the intranasal administration of amino group functionalized GQDs (A-GQDs) was observed to enhance the number of neuronal cell death, trigger ferroptosis activities, i.e. ferrous iron overload and lipid peroxidation as well as cause inflammatory reactions in hippocampus. Meanwhile, these adverse effects were found in BV2 microglial cells treated with A-GQDs, which were all attenuated by a ferroptosis-specific inhibitor ferrostain-1 (Fer-1). The inflammatory responses to A-GQDs in BV2 cells were evidenced as the increased secretion of pro-inflammatory cytokine TNF-α that was attributed to the high mobility group box 1 (HMGB1) released from ferroptosis-occurred cells. The nuclear transference of yes-associated protein (YAP), an effector in Hippo signaling pathway, regulated by the phosphorylation of p38 mitogen-activated protein kinase (MAPK) was then found to play a critical role in A-GQDs triggering ferroptosis through transcriptionally mediating transferrin receptor protein (TFRC) and arachidonate lipoxygenase 3 (ALOXE3) to increase levels of ferrous iron and lipid peroxides, respectively. The findings not only highlight the importance of risk assessments on QDs containing low toxic component, but also provide toxic biomarkers for the interventions of GQDs in the brain.