Femtosecond laser ablation of highly oriented pyrolytic graphite: a green route for large-scale production of porous graphene and graphene quantum dots

2-Dimensional graphene as a route for emergence of additional dimension nanomaterials

Dimension has a different and impactful significance in the field of innovation, research and technologies. Starting from one-dimension, now, we all are moving towards 3-D visuals and try to do the things in this dimension. However, we still have some very innovative and widely applicable nanomaterials, which have tremendous potential in the form of 2-D only i.e. graphene. In this review, we have tried to incorporate the reported pathways used so far for modification of 2-D graphene sheets to make is three-dimensional. The modified graphene been applied in many fields like supercapacitors, sensors, catalysis, energy storage devices and many more. In addition, we have also incorporated the conversion of 2-D graphene to their various other dimensions like zero-, one- or three-dimensional nanostructures.

Green and Tunable Decoration of Graphene with Spherical Nanoparticles Based on Laser Ablation in Water: A Case of Ag Nanoparticle/Graphene Oxide Sheet Composites

A simple and green strategy is presented to decorate graphene with nanoparticles, based on laser ablation of targets in graphene auqeous solution. Ag and graphene oxide (GO) are chosen as model materials. The surface of GO sheets is strongly anchored with spherical Ag nanoparticles. The density and size of the Ag nanoparticles can be easily tuned by laser ablation conditions. Further, the GO sheets can be decorated with other nanoparticles from simple metals or semiconductors to multicomponent hybrids. Additionally, the Ag nanoparticle/GO sheet colloids can be utilized as blocks to build three-dimensional structures, such as sandwich membranes by evaporation-induced self-assembly. These graphene-based composite materials could be very useful in catalysis, sensors, and nanodevices. Particularly, the Ag nanoparticle/GO sheet sandwich composite membranes exhibit excellent surface-enhanced Raman scattering performance and possess the huge potential in trace-detecting persistent organic pollutants in the environment.

Introduction of selectivity and specificity to graphene using an inimitable combination of molecular imprinting and nanotechnology

Recently, the nanostructured modified molecularly imprinting polymer has created a great attention in research field due to its excellent properties such as high surface to volume ratio, low cost, and easy preparation/handling. Among the nanostructured materials, the carbonaceous material such as 'graphene' has attracted the tremendous attention of researchers owing to their fascinating electrical, thermal and physical properties. In this review article, we have tried to explore as well as compile the role of graphene-based nanomaterials in the fabrication of imprinted polymers. In other words, herein the recent efforts made to introduce selectivity in graphene-based nanomaterials were tried collected together. The major concern of this review article is focused on the sensing devices fabricated via a combination of graphene, graphene@nanoparticles, graphene@carbon nanotubes and molecularly imprinted polymers. Additionally, the combination of graphene and quantum dots was also included to explore the fluorescence properties of zero-band-gap graphene.

Solid-phase synthesis of graphene quantum dots from the food additive citric acid under microwave irradiation and their use in live-cell imaging

The work demonstrated that solid citric acid, one of the most common food additives, can be converted to graphene quantum dots (GQDs) under microwave heating. The as-prepared GQDs were further characterized by various analytical techniques like transmission electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, fluorescence and UV-visible spectroscopy. Cytotoxicity of the GQDs was evaluated using HeLa cells. The result showed that the GQDs almost did not exhibit cytotoxicity at concentrations as high as 1000 µg mL(-1). In addition, it was found that the GQDs showed good solubility, excellent photostability, and excitation-dependent multicolor photoluminescence. Subsequently, the multicolor GQDs were successfully used as a fluorescence light-up probe for live-cell imaging.

Facile Synthesis of Molecularly Imprinted Graphene Quantum Dots for the Determination of Dopamine with Affinity-Adjustable

A facilely prepared fluorescence sensor was developed for dopamine (DA) determination based on polyindole/graphene quantum dots molecularly imprinted polymers (PIn/GQDs@MIPs). The proposed sensor exhibits a high sensitivity with a linear range of 5 × 10(-10) to 1.2 × 10(-6) M and the limit of detection as low as 1 × 10(-10) M in the determination of DA, which is probably due to the tailor-made imprinted cavities for binding DA thought hydrogen bonds between amine groups of DA and oxygen-containing groups of the novel composite. Furthermore, the prepared sensor can rebind DA in dual-type: a low affinity type (noncovalent interaction is off) and a high affinity type (noncovalent interaction is on), and the rebinding interaction can be adjusted by tuning the pH, which shows a unique potential for adjusting the binding interaction while keeping the specificity, allowing for wider applications.

Laser-ablation production of graphene oxide nanostructures: from ribbons to quantum dots

A new one-step method for the preparation of graphene oxide (GO) nanostructures has been developed by pulsed laser ablation in GO solution. The formation of different shapes of GO nanostructures, such as ribbons, nanoflakes (including nano-squares, nano-rectangles, nano-triangles, nano-hexagons, and nano-disks) and quantum dots, has been demonstrated by scanning electron microscopy and transmission electron microscopy. Photoreduction for the GO occurred during irradiation by the pulsed laser. The GO quantum dots exhibit a blue photoluminescence, originating from recombination of the localized carriers in the zigzag-edge states.

Preparation of fluorescent graphene quantum dots from humic acid for bioimaging application

Humic acid as a raw material was applied for the preparation of graphene quantum dots by a one-step hydrothermal method.

One-step hydrothermal synthesis and optical properties of PEG-passivated nitrogen-doped carbon dots

PEG-passivation enhanced the luminescence intensity of nitrogen-doped carbon dots markedly.

Electrochemical synthesis of small-sized red fluorescent graphene quantum dots as a bioimaging platform

We report water-soluble, 3 nm uniform-sized graphene quantum dots (GQDs) with red emission prepared by electrochemical exfoliation of graphite in K₂S₂O₈ solution. Such GQDs show a great potential as biological labels for cellular imaging.

Strategy and mechanism for controlling the direction of defect evolution in graphene: preparation of high quality defect healed and hierarchically porous graphene

In this paper, a novel approach for controlling the direction of defect evolution in graphene through intercalation of organic small molecules into graphite oxide (GO) combined with a one-pot microwave-assisted reaction is reported. By using ethanol as intercalator, the bulk production of high quality graphene with its defects being satisfactorily healed is achieved. The repair of defects using extraneous carbon atoms and the hybrid state of these carbon atoms are definitely demonstrated using isotopic tracing studies with (13)C-labeled ethanol combined with (13)C solid-state NMR. The defect healed graphene shows excellent crystallinity, extremely low oxygen content (C : O ratio of 23.8) and has the highest sheet conductivity (61 500 S m(-1)) compared to all other reported graphene products derived from GO. By using methanol or benzene as intercalators, hierarchically porous graphene with a self-supported 3-dimensional framework (∼917 m(2) g(-1)) containing both macropores and mesopores (2-5 nm) is obtained. This graphene possesses a distinctive amorphous carbon structure around the edge of the nanopores, which could be conducive to enhancing the lithium storage performance (up to 580 mA h g(-1) after 300 cycles) when tested as an anode of lithium ion batteries, and might have promising applications in the field of electrode materials, catalysis, and separation, and so on. The mechanism involved for the controlled defect evolution is also proposed. The simple, ultrafast and unified strategy developed in this research provides a practical and effective approach to harness structural defects in graphene-based materials, which could also be expanded for designing and preparing other ordered carbon materials with specific structures.

Facile synthesis of TiN decorated graphene and its enhanced catalytic effects on dehydrogenation performance of magnesium hydride

TiN@rGO nanohybrids were successfully synthesized by a simple "urea glass" technique. Experimental results demonstrated that TiN nanocrystals, with an average particle size of 20 nm, were uniformly anchored onto highly reduced graphene nanosheets. The as-synthesized TiN@rGO nanohybrids showed a porous planar-like structure, which had a large surface area of 177 m(2) g(-1). More importantly, the as-prepared TiN@rGO hybrids showed enhanced catalytic effects on the dehydrogenation of MgH2. The dehydrogenation thermodynamics and kinetics of the MgH2-TiN@rGO composites were systematically investigated and some significant improvements were confirmed. It was found that the 10 wt% TiN@rGO doped MgH2 sample started to release hydrogen at about 167 °C, and roughly 6.0 wt% hydrogen was released within 18 min when isothermally heated to 300 °C. In contrast, the onset dehydrogenation temperature of the pure MgH2 sample was about 307 °C, and only 3.5 wt% hydrogen was released even after 120 min of heating under identical conditions. In addition, the catalytic mechanism of TiN@rGO on the dehydrogenation of MgH2 was discussed using the Johnson-Mehl-Avrami (JMA) model and X-ray diffraction equipment.

Synthesis and optical properties of nitrogen and sulfur co-doped graphene quantum dots

Schematic and digital photos of the preparation for water-soluble nitrogen (N) and sulfur (S) co-doped graphene quantum dots (NS-GQDs). Sulfur enhances the photoluminescence of NS-GQDs.

Organosilane-functionalized graphene quantum dots and their encapsulation into bi-layer hollow silica spheres for bioimaging applications

We demonstrate an affordable method to fabricate organosilane-functionalized graphene quantum dots and their encapsulation into bi-layer hollow silica spheres for bioimaging applications.