ABSTRACT
This paper reports the effect of graphene encapsulation on the thermal stability of DNA nanostructures and the thermal oxidation of graphene in the presence of DNA nanostructures. Triangular-shaped DNA nanostructures were deposited onto a Si/SiO2 substrate and covered with single-layer graphene. The apparent height of the DNA nanostructure significantly decreased upon thermal annealing at 250 °C and higher temperatures. The topographical features of the DNA nanostructure, as measured by atomic force microscopy (AFM), disappeared after annealing at 300 °C for 5 h but reappeared after 23 h. In contrast, in the absence of a graphene coating, the topographical features of DNA nanostructure disappeared after heating at 300 °C for 45 min. After heating at 300 °C for 29 h, oxidation produced nanometer-sized holes on graphene, some of which were triangular and spatially overlapped with DNA nanostructures. These results suggest that the inorganic residues produced by the decomposition of DNA nanostructures enhance the oxidation of graphene in a site-specific manner.
Subject(s)
DNA/chemistry , Graphite/chemistry , Nanostructures/chemistry , Hot Temperature , Nucleic Acid Conformation , Oxidation-Reduction , Silicon/chemistry , Silicon Dioxide/chemistry , Surface PropertiesABSTRACT
Fluorescent organic dyes photobleach under intense light. Graphene has been shown to improve the photo-stability of organic dyes. In this paper, we investigated the Raman spectroscopy and photo-bleaching kinetics of dyes in the absence/presence of chemical vapor deposition (CVD)-grown graphene. We show that graphene enhances the Raman signal of a wide range of dyes. The photo-bleaching of the dyes was reduced when the dyes were in contact with graphene. In contrast, monolayer hexagonal boron nitride (h-BN) was much less effective in reducing the photo-bleaching rate of the dyes. We attribute the suppression of photo-bleaching to the energy or electron transfer from dye to graphene. The results highlight the potential of CVD graphene as a substrate for protecting and enhancing Raman response of organic dyes.
ABSTRACT
We report the deposition of DNA origami nanostructures on highly oriented pyrolytic graphite (HOPG). The DNA origami goes through a structural rearrangement and the DNA base is exposed to interact with the graphite surface. Exposure to ambient air, which is known to result in a hydrophilic-to-hydrophobic wetting transition of HOPG, does not significantly impact the deposition yield or the shape deformation of DNA nanostructures. The deposited DNA nanostructures maintain their morphology for at least a week and promote site-selective chemical vapor deposition of SiO2. This process is potentially useful for a range of applications that include but are not limited to nanostructure fabrication, sensing, and electronic and surface engineering.
Subject(s)
DNA/chemistry , Graphite/chemistry , Nanostructures/chemistry , DNA, Single-Stranded/chemistry , Nucleic Acid Conformation , Silicon Dioxide/chemistry , WettabilityABSTRACT
DNA nanostructures are versatile templates for low cost, high resolution nanofabrication. However, due to the limited chemical stability of pure DNA structures, their applications in nanofabrication have long been limited to low temperature processes or solution phase reactions. Here, we demonstrate the use of DNA nanostructure as a template for high temperature, solid-state chemistries. We show that programmably shaped carbon nanostructures can be obtained by a shape-conserving carbonization of DNA nanostructures. The DNA nanostructures were first coated with a thin film of Al2O3 by atomic layer deposition (ALD), after which the DNA nanostructure was carbonized in low pressure H2 atmosphere at 800-1000 °C. Raman spectroscopy and atomic force microscopy (AFM) data showed that carbon nanostructures were produced and the shape of the DNA nanostructure was preserved. Conductive AFM measurement shows that the carbon nanostructures are electrically conductive.
Subject(s)
Carbon/chemistry , DNA/chemistry , Nanostructures/chemistry , Electric Conductivity , Hot Temperature , Microscopy, Atomic Force , Nanostructures/ultrastructure , Nanotechnology/methodsABSTRACT
We report an ultrasound exfoliation of graphite in a weakly basic solution to produce multi-layer graphene dispersion. A unique feature of this process is that no surfactant was added to stabilize the exfoliated graphene in water. The concentration of the graphene dispersion prepared by this approach can be up to 0.02 mg mL(-1) and it was stable at room temperature for several months.
