rGO Nanostructures Research Articles

Fe3O4@Au/reduced graphene oxide nanostructures: Combinatorial effects of radiotherapy and photothermal therapy on oral squamous carcinoma KB cell line

Combination therapy including radiotherapy (RT) and photothermal therapy (PTT), as an alternative treatment for cancer treatment, recently has generated substantial interest. Graphene-based nanocarbons and gold content metallic nanoparticles, as one of the most attractive materials with their extraordinary physical and chemical properties, are extremely useful in this regard. We herein reported the effects of combination of cancer therapy including RT (doses of 2 and 4 Gy) and PTT (808 nm laser irradiation, NIR irradiation) as radio-photothermal therapy (RPTT) of KB oral squamous carcinoma cell line in the presence of Fe3O4@Au/reduced graphene oxide (rGO) nanostructures (NSs) at different concentrations. Fe3O4@Au/rGO NSs with different rGO contents have been synthesized by hydrothermal reaction method. They characterized by XRD, FE-SEM, TEM, EDS, FTIR and TGA. Cell viability for cytotoxicity, RT, PTT and RPTT were studied by MTT (3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay. High photothermal conversion efficiency of Fe3O4@Au/rGO NSs reaches to 61%. The resulting Fe3O4@Au NPs with approximate size of about 10–60 nm covered the rGO nanosheets with 40 wt% rGO at concentration of 20 μg ml−1, exhibited satisfactory cytotoxicity. They provided significant cell destruction under RT, PTT and specially RPTT in dose of 4 Gy. Furthermore, they have good biocompatibility on the healthy cells. Our results show that Fe3O4@Au/rGO NSs integrated with radiosensitization, photothermal therapy and their combination promising for nanomedicine and clinical applications.

Interaction and Reactivity of Cisplatin Physisorbed on Graphene Oxide Nano-Prototypes.

The physical adsorption of cisplatin (CP) on graphene oxide (GO) and reduced graphene oxide (rGO) is investigated at the DFT level of theory by exploiting suitable molecular prototypes representing the most probable adsorbing regions of GO and rGO nano-structures. The results show that the CP binding energy is enhanced with respect to that for the interaction with pristine graphene. This is due to the preferential adsorption of the drug in correspondence of the epoxy and hydroxy groups located on GO basal plane: an energy decomposition analysis of the corresponding binding energy reveals that the most attractive contribution comes from the electrostatic attraction between the -NH ends of CP and the oxygen groups on (r)GO, which can be associated with hydrogen bonding effects. Moreover, it is found that the reactivity of the physically adsorbed CP is practically unaltered being the free energy variation of the first hydrolysis reaction almost matching that of its free (unadsorbed drug) counterpart. The reported results suggest that the CP physical adsorption on GO and rGO carriers is overall feasible being an exergonic process in aqueous solution. The CP adsorption could facilitate its solubility and transport in water solutions, exploiting the high hydrophilicity of the peripheral carboxylic groups located on the edge of the GO and rGO nano-structures. Moreover, the the higher affinity of CP with respect to the oxidized sites suggests a possible dependence of drug loading and release on pH conditions, which would highly facilitate its specific delivery.

Three-dimensional hierarchical Ni5P4 nanospheres encapsulated in graphene as high-performance anode materials of sodium ion batteries

Transition metal phosphides have received extensive attention as anode materials of sodium ion batteries due to their high theoretical specific capacity and low redox potentials. However, the large volume change during the insertion/extraction of sodium ions often leads to a poor electrochemical performance and thus limits their practical application. Herein, we rationally designed three-dimensional hierarchical Ni5P4 nanospheres wrapped by rGO nanostructures (Ni5P4@rGO) through a sequential hydrothermal synthesis and phosphidation of highly folded spherical α-Ni(OH)2. The graphene nanosheets can effectively prevent the collapse of spherical α-Ni(OH)2 and aggregation of Ni5P4 active materials during phosphidation. Besides, the strong coupling between the nickel phosphide and graphene layers leads to excellent electrochemical performance of Ni5P4@rGO composite as anode materials of SIBs, delivering a specific capacity of 304 mA h g–1 at 0.2 A g–1 after 200 cycles. The strategy developed in this paper may shed light on the morphology-controlled synthesis of transition metal phosphides with high performance for energy storage devices.

Lipid-Functionalized Graphene Loaded with hMnSOD for Selective Inhibition of Cancer Cells.

Combination therapies utilize multiple mechanisms to target cancer cells to minimize cancer cell survival. Graphene provides an ideal platform for combination therapy due to its photothermal properties and high loading capacity for cancer-fighting molecules. Lipid functionalization of graphene extends its potential as a therapeutic platform by improving its biocompatibility and functionality. Previous studies involving graphene demonstrated its usage as a therapeutic vehicle; however, the effect of bare and engineered graphene structures on oxidative stress has not been comprehensively investigated. Because oxidative stress has been linked to cancer progression, it is vital to examine the generation of reactive oxygen species (ROS) in response to therapeutic platforms. This study functionalizes reduced graphene oxide (rGO) with lipids and the antioxidant enzyme human manganese superoxide dismutase (hMnSOD) and presents a detailed characterization of cellular responses to bare and functionalized rGO nanostructures in tumorigenic and nontumorigenic breast cell lines. Each cell type displayed distinct responses depending on whether they were normal, nonmetastatic, or metastatic cells. Bare rGO significantly reduced cell growth and substantially increased ROS production in all cell lines and instigated necrosis in metastatic breast cancer cells. Cell proliferation decreased in cancerous breast cells upon introduction of lipid-rGO, which correlated with peroxidation of lipids coating the rGO. In contrast, lipid-rGO nanostructures had minimal impact on proliferation and lipid peroxidation for normal breast cells. Lipid-rGO nanostructures with bound hMnSOD inhibited the proliferation of metastatic cancer cells while preventing necrosis and avoiding the negative side effects on normal cells associated with chemotherapeutic agents. Together, the results confirm the importance of functionalizing rGO for therapeutic applications and present an additional modality for the usage of graphene to selectively target cancer cells.

Effect of pH-Responsive Charge-Conversional Polymer Coating to Cationic Reduced Graphene Oxide Nanostructures for Tumor Microenvironment-Targeted Drug Delivery Systems.

Tumor tissue represents a slightly acidic pH condition compared to normal tissue due to the accumulation of lactic acids via anaerobic metabolism. In this work, pH-responsive charge-conversional polymer (poly(ethylene imine)-poly(l-lysine)-poly(l-glutamic acid), PKE polymer) was employed for endowing charge-conversional property and serum stability to poly(ethylene imine) conjugated reduced graphene oxide-based drug delivery system (PEI-rGO). Zeta-potential value of PEI-rGO coated with PK5E7 polymer (PK5E7(PEI-rGO)) was −10.9 mV at pH 7.4 and converted to 29.2 mV at pH 6.0, showing pH-responsive charge-conversional property. Sharp-edged plate morphology of PEI-rGO was transformed to spherical nanostructures with vague edges by PK5E7 coating. Size of PK5E7(PEI-rGO) was found to be smaller than that of PEI-rGO in the serum condition, showing its increased serum stability. Loaded doxorubicin (DOX) in PK5E7(PEI-rGO) could be released rapidly in lysosomal condition (pH 5.0, 5 mM glutathione). Furthermore, DOX-loaded PK5E7(PEI-rGO) showed enhanced anticancer activity in HeLa and A549 cells in the tumor microenvironment-mimicking condition (pH 6.0, serum), which would be mediated by non-specific cellular interaction with decorated serum proteins. These results indicate that the pH-responsive charge-conversional PKE polymer coating strategy of cationic rGO nanostructures possesses a potential for acidic tumor microenvironment-targeted drug delivery systems.

RETRACTED ARTICLE: Engineered organic halide perovskite solar cells by incorporation of surface-manipulated graphenic nanosheets

The reduced graphene oxide (rGO) and rGO-g-poly(3-dodecyl thiophene) (PDDT) precursors were applied in the active layers of CH3NH3PbI3 perovskite solar cells. The rGO-g-PDDT modified perovskite devices represented the lower charge-transfer resistance (31.8 Ω cm2), higher short circuit current density (20.86 mA/cm2) and thus the larger performance (14.07%) compared with the pristine (74.2 Ω cm2, 17.90 mA/cm2, 11.10%) and rGO-incorporated devices (82.4 Ω cm2, 13.65 mA/cm2, 8.00%). The grafted-rGO components improved the cell characteristics, whereas the bared rGO nanostructures ruined them. The narrow distribution and thereby the high reproducibility and high performance in perovskite + rGO-g-PDDT photovoltaics were attributed to the improved morphology and enhanced grain size (190 nm vs 400 nm), progressed optical absorbance, and enhanced crystallinity of the CH3NH3PbI3 perovskites through the incorporation of rGO-g-PDDT modifiers.

Facile spray drying approach to synthesize Sb2Se3/rGO composite anode for lithium-ion battery

Novel Sb2Se3/reduced graphene oxide (rGO) composite, 1D Sb2Se3 nanorods wrapped with rGO, has been successfully synthesized by a facile spray drying method. Compared to as-prepared Sb2Se3 nanorods, the obtained Sb2Se3/rGO composite, as anode for lithium-ion batteries (LIBs), exhibited super electrochemical performances. The results suggest that Sb2Se3/rGO composite can retain a reversible capacity of 394 mAh g−1 over 200 cycles at 100 mA g−1 between 0.01 and 3 V (vs Li/Li+). Even at a high rate current density of 1000 mA g−1, a discharge capacity of 247 mAh g−1 was computed, indicating that this LIB possesses good rate capability. This improved electrochemical performance can be attributed to the 1D nanostructure, and also to the introduction of rGO, which provided more electron transport pathways and shortened the Li-ion diffusion through the electrolyte. Consequently, the cluster of 1D Sb2Se3 nanorods that are wrapped in the rGO nanostructure can efficiently buffer large volume changes and retain the structural stability during lithiation and delithiation process, resulting in an excellent electrochemical performance.

Purposive Assembling of Poly(3-hexylthiophene) onto Chemically Treated Multi-Wall Carbon Nanotube versus Reduced Graphene Oxide

Surfaces of multi-walled carbon nanotubes (CNTs) and reduced graphene oxide (rGO) nanosheets were chemically modified to design distinct donor-acceptor nano-hybrids having different morphologies and orientations. In unmodified CNTs and their derivatives functionalized with 2-hydroxymethyl thiophene (CNT-f-COOTh) and grafted with poly(3-dodecylthiophene) (CNT-g-PDDT), double-fibrillar, shishkebab, and stem-leaf nanostructures were decorated. Furthermore, rGO nanosheets functionalized with 2-thiophene acetic acid (rGO-f-TAA) and grafted with poly(3-dodecylthiophene) (rGO-g-PDDT) were prepared to study differences in CNT and rGO supramolecules. Three types of orientations subsuming face-on, edge-on, and flat-on were detected in nano-hybrids based on CNT and rGO. Morphology (fibrillar) and orientation (face-on) of poly(3-hexylthiophene) (P3HT) assemblies were similar onto unmodified CNT and rGO nanostructures. Although patternings of P3HT chains were completely different onto functionalized CNT and rGO (shish-kebab versus nanocrystal decorated nanosheets), edge-on orientation was detected in CNT-f-COOTh/P3HT and rGO-f-TAA/P3HT nano-hybrids. In CNT-g-PDDT/P3HT and rGO-g-PDDT/P3HT systems, P3HT chains were extendedly assembled onto grafted carbonic materials; however, their different natures reflected stem-leaf and patched-like configurations, respectively. For unmodified, functionalized, and grafted CNT and rGO patterned with P3HT chains, a photoluminescence quenching was detected for a donor-acceptor nature. Owing to flat-on oriented P3HTs, the best photoluminescence quenching, thereby the best donating-accepting features were detected for CNT-g-PDDT/P3HT and rGO-g-PDDT/P3HT supramolecules.

Effects of gallic acid biofabricated rGO nanosheets combined with radiofrequency radiation for the treatment of renal cell carcinoma

The combination of biologically active compounds and nanomaterials in biomedicine field is growing rapidly and provided excellent forecasts for the progress of facile non-invasive approaches for the diagnosis of cancer therapy. In this present study, we demonstrated that as-prepared gallic acid (GA) coated reduced graphene oxide (rGO) combined with radiofrequency (RF) ablation has facilitated for the treatment of human renal epithelial cancer (A-489) cells without disturbing the renal proximal epithelial (HK−2) cells. The successful biofabrication of GA onto the rGO nanostructure has been elaborated with the support of peak intensities of diffracted X-ray patterns and Raman spectral visualizations. The micrograph imageries are displayed that the warped and ribbed structure containing wrinkled paper-like arrangement with multilayer structure of rGO with assistance of GA molecules. The synthesized GA-rGO nanomaterials exhibited a very good apoptosis and toxic effect on A-489 renal cancer cells, which was found to exhibit enhanced tumor cytotoxicity in RF combination treatment compared to RF treated alone. Moreover, the results are highly cheering to go for functionalized nanomaterial and RF radiation, combined drug delivery system to overcome the limitation to treat kidney cancers.

Development of highly faceted reduced graphene oxide-coated copper oxide and copper nanoparticles on a copper foil surface

This work describes the formation of reduced graphene oxide-coated copper oxide and copper nanoparticles (rGO-Cu2ONPs, rGO-CuNPs) on the surface of a copper foil supporting graphene oxide (GO) at annealing temperatures of 200–1000 °C, under an Ar atmosphere. These hybrid nanostructures were developed from bare copper oxide nanoparticles which grew at an annealing temperature of 80 °C under nitrogen flux. The predominant phase as well as the particle size and shape strongly depend on the process temperature. Characterization with transmission electron microscopy and scanning electron microscopy indicates that Cu or Cu2O nanoparticles take rGO sheets from the rGO network to form core–shell Cu–rGO or Cu2O–rGO nanostructures. It is noted that such ones increase in size from 5 to 800 nm as the annealing temperature increases in the 200–1000 °C range. At 1000 °C, Cu nanoparticles develop a highly faceted morphology, displaying arm-like carbon nanorods that originate from different facets of the copper crystal structure.

Efficient NiSe-Ni3Se2/Graphene Electrocatalyst in Dye-Sensitized Solar Cells: The Role of Hollow Hybrid Nanostructure.

Hollow and hybrid nanomaterials are excellent electrocatalysts on account of their novel electrocatalytic properties compared with homogeneous solid nanostructures. In this report, NiSe-Ni3Se2 hybrid nanostructure with morphology of hollow hexagonal nanodisk was synthesized in situ on graphene. A series of NiSe-Ni3Se2/RGO with different phase constitutions and nanostructures were obtained by controlling the durations of solvothermal treatment. Because of their unique hollow and hybrid structure, NiSe-Ni3Se2/RGO hollow nanodisks exhibited higher electrocatalytic performance than NiSe/RGO and solid NiSe-Ni3Se2/RGO nanostructure for reducing I3(-) as counter cell (CE) of dye-sensitized solar cells (DSSCs). Additionally, NiSe-Ni3Se2/RGO hollow nanodisks achieved much lower charge transfer resistance (Rct = 0.68 Ω) and higher power conversion efficiency (PCE) (7.87%) than those of Pt (Rct = 1.41 Ω, PCE = 7.28%).

Catalytic tailoring of large-area reduced graphene oxide by tunable arrays of Pt nanostructures synthesized from self-assembling diblock copolymers

In this study, the large-area tailoring of reduced graphene oxide (rGO) with tunable arrays of Pt nanostructures has been demonstrated. We synthesized arrays of catalytic Pt nanoparticles, nanowires, and their combined nanostructures from self-assembled thin films of polystyrene-block-poly(4-vinylpyridine) copolymers and their micelles. Then, rGO was transferred onto these Pt nanostructures, which were capable of catalyzing the oxidative elimination of carbon atoms from the rGO nanoregions in contact with the Pt, resulting in successful pattern transfer from the Pt nanoarrays onto the rGO, forming various nanostructures, such as nanoholes, nanoribbons, and perforated nanoribbons. Moreover, we transferred the tailored rGO onto a transparent and flexible polymeric substrate. The size and periodicity of the rGO nanostructures were controlled on the nanometer scale by adjusting those of the Pt nanostructures, which were strongly dependent on the molecular weights of the copolymers. In addition, arrayed Pt nanowires were aligned in a topographically patterned substrate by the directed self-assembly of the copolymers, enabling the fabrication of well-aligned rGO nanoribbon and nanosquare arrays.

Assembly of thermally reduced graphene oxide nanostructures by alternating current dielectrophoresis as hydrogen-gas sensors

Chemo-resistive hydrogen-gas sensors based on thermally reduced graphene oxide (rGO) have been fabricated on a micro-hotplate by positive ac dielectrophoresis (DEP). The optimized DEP parameters for manipulating rGO nanostructures into Au electrodes for hydrogen sensing are: applied frequency = 1 MHz, peak-to-peak voltage = 5 V, and DEP time = 30 s. The device exhibits good sensitivity (∼6%) with fast response time (∼11 s) and recovery time (∼36 s) for 200 ppm hydrogen gas at room temperature. This result indicates that the DEP process has great potential for assembling rGO for hydrogen-gas sensor in many industrial and scientific applications.