Pristine graphene quantum dots and graphene oxide quantum dots are synthesized by chemical exfoliation from the graphite nanoparticles with high uniformity in terms of shape (circle), size (less than 4 nm), and thickness (monolayer). The origin of the blue and green photoluminescence of GQDs and GOQDs is attributed to intrinsic and extrinsic energy states, respectively.

In this study, we demonstrated the potential of graphene nanomaterials as environmental pollutant adsorbents by utilizing the characteristics of ultralarge surface area and strong π-π interaction on the surface. We generated a three-dimensional (3D) graphene oxide sponge (GO sponge) from a GO suspension through a simple centrifugal vacuum evaporation method, and used them to remove both the methylene blue (MB) and methyl violet (MV) dyes which are main contaminants from the dye manufacturing and textile finishing. The efficiency and speed of dye adsorption on a GO sponge was investigated under various parameters such as contact time, stirring speed, temperature, and pH. The adsorption process shows that 99.1% of MB and 98.8% of MV have been removed and the equilibrium status has been reached in 2 min. The 3D GO sponge displays adsorption capacity as high as 397 and 467 mg g(-1) for MB and MV dye, respectively, and the kinetic data reveal that the adsorption process of MB and MV dyes is well-matched with the pseudo second-order model. The MB and MV adsorption on the 3D GO sponge involved in endothermic chemical adsorption through the strong π-π stacking and anion-cation interaction with the activation energy of 50.3 and 70.9 kJ mol(-1), respectively. The 3D GO sponge has demonstrated its high capability as an organic dye scavenger with high speed and efficiency.

Don′t FRET when I GO: Sensitive and selective rotavirus detection is achieved by using the photoluminescence of a graphene oxide (GO) array. The target cell was captured by the rotavirus‐specific antibody immobilized on the GO array, and the binding event was monitored by observing the fluorescence quenching that results from fluorescence resonance energy transfer (FRET) between GO and gold nanoparticles linked to the antibodies (see picture).

A portable forensic genetic analysis system consisting of a microfluidic device for amplification and separation of short tandem repeat (STR) fragments as well as an instrument for chip operation and four-color fluorescence detection has been developed. The microdevice performs polymerase chain reaction (PCR) in a 160-nL chamber and capillary electrophoresis (CE) in a 7-cm-long separation channel. The instrumental design integrates PCR thermal cycling, electrophoretic separation, pneumatic valve fluidic control, and four-color laser excited fluorescence detection. A quadruplex Y-chromosome STR typing system consisting of amelogenin and three Y STR loci (DYS390, DYS393, DYS439) was developed and used for validation studies. The multiplex amplification of these 4 loci with 35 PCR cycles followed by CE separation and 4-color fluorescence detection was completed in 1.5 h. All the amplicons can be detected with a limit of detection of 20 copies of male standard DNA in the reactor. Real-world forensic analyses of oral swab and human bone extracts from case evidence were also successfully performed. Mixture analysis demonstrated that a balanced profile can be obtained even at a male-to-female template ratio of 1:10. The successful development and operation of this portable PCR-CE system establishes the feasibility of rapid point-of-analysis DNA typing of forensic casework, of mass disaster samples or of individuals at a security checkpoint.

A simple method to prepare large‐scale graphene sponges and free‐standing graphene films using a speed vacuum concentrator is presented. During the centrifugal evaporation process, the graphene oxide (GO) sheets in the aqueous suspension are assembled to generate network‐linked GO sponges or a series of multilayer GO films, depending on the temperature of a centrifugal vacuum chamber. While sponge‐like bulk GO materials (GO sponges) are produced at 40 °C, uniform free‐standing GO films of size up to 9 cm2 are generated at 80 °C. The thickness of GO films can be controlled from 200 nm to 1 µm based on the concentration of the GO colloidal suspension and evaporation temperature. The synthesized GO films exhibit excellent transparency, typical fluorescent emission signal, and high flexibility with a smooth surface and condensed density. Reduced GO sponges and films with less than 5 wt% oxygen are produced through a thermal annealing process at 800 °C with H2/Ar flow. The structural flexibility of the reduced GO sponges, which have a highly porous, interconnected, 3D network, as well as excellent electrochemical properties of the reduced GO film with respect to electrode kinetics for the [Fe(CN)6]3−/4− redox system, are demonstrated.