22 research outputs found
A new bifunctional hybrid nanostructure as an active platform for photothermal therapy and MR imaging
As a bi-functional cancer treatment agent, a new hybrid nanostructure is presented which can be used for photothermal therapy by exposure to one order of magnitude lower laser powers compared to similar nanostructures in addition to substantial enhancment in magnetic resonance imaging (MRI) contrast. This gold-iron oxide hybrid nanostructure (GIHN) is synthesized by a cost-effective and high yield water-based approach. The GIHN is sheilded by PEG. Therefore, it shows high hemo and biocompatibility and more than six month stability. Alongside earlier nanostructures, the heat generation rate of GIHN is compareable with surfactnat-capped gold nanorods (GNRs). Two reasons are behind this enhancement: Firstly the distance between GNRs and SPIONs is adjusted in a way that the surface plasmon resonance of the new nanostructure is similar to bare GNRs and secondly the fraction of GNRs is raised in the hybrid nanostructure. GIHN is then applied as a photothermal agent using laser irradiation with power as low as 0.5 W.cm−2 and only 32% of human breast adenocarcinoma cells could survive. The GIHN also acts as a dose-dependent transvers relaxation time (T2) MRI contrast agent. The results show that the GINH can be considered as a good candidate for multimodal photothermal therapy and MRI
The catalytic potential of high-k dielectrics for graphene formation
The growth of single and multilayer graphene nano-flakes on MgO and ZrO2 at
low temperatures is shown through transmission electron microscopy. The
graphene nano-flakes are ubiquitously anchored at step edges on MgO (100)
surfaces. Density functional theory investigations on MgO (100) indicate C2H2
decomposition and carbon adsorption at step-edges. Hence, both the experimental
and theoretical data highlight the importance of step sites for graphene growth
on MgO
Graphene: Piecing it together
Graphene has a multitude of striking properties that make it an exceedingly
attractive material for various applications, many of which will emerge over
the next decade. However, one of the most promising applications lie in
exploiting its peculiar electronic properties which are governed by its
electrons obeying a linear dispersion relation. This leads to the observation
of half integer quantum hall effect and the absence of localization. The latter
is attractive for graphene-based field effect transistors. However, if graphene
is to be the material for future electronics, then significant hurdles need to
be surmounted, namely, it needs to be mass produced in an economically viable
manner and be of high crystalline quality with no or virtually no defects or
grains boundaries. Moreover, it will need to be processable with atomic
precision. Hence, the future of graphene as a material for electronic based
devices will depend heavily on our ability to piece graphene together as a
single crystal and define its edges with atomic precision. In this progress
report, the properties of graphene that make it so attractive as a material for
electronics is introduced to the reader. The focus then centers on current
synthesis strategies for graphene and their weaknesses in terms of electronics
applications are highlighted.Comment: Advanced Materials (2011
Identification of semiconductive patches in thermally processed monolayer oxo‐functionalized graphene
The thermal decomposition of graphene oxide (GO) is a complex process at the atomic level and not fully understood. Here, a subclass of GO, oxo‐functionalized graphene (oxo‐G), was used to study its thermal disproportionation. We present the impact of annealing on the electronic properties of a monolayer oxo‐G flake and correlated the chemical composition and topography corrugation by two‐probe transport measurements, XPS, TEM, FTIR and STM. Surprisingly, we found that oxo‐G, processed at 300 °C, displays C−C sp3‐patches and possibly C−O−C bonds, next to graphene domains and holes. It is striking that those C−O−C/C−C sp3‐separated sp2‐patches a few nanometers in diameter possess semiconducting properties with a band gap of about 0.4 eV. We propose that sp3‐patches confine conjugated sp2‐C atoms, which leads to the local semiconductor properties. Accordingly, graphene with sp3‐C in double layer areas is a potential class of semiconductors and a potential target for future chemical modifications
Recommended from our members
Synthesis of carbon nanotubes with and without catalyst particles
The initial development of carbon nanotube synthesis revolved heavily around the use of 3d valence transition metals such as Fe, Ni, and Co. More recently, noble metals (e.g. Au) and poor metals (e.g. In, Pb) have been shown to also yield carbon nanotubes. In addition, various ceramics and semiconductors can serve as catalytic particles suitable for tube formation and in some cases hybrid metal/metal oxide systems are possible. All-carbon systems for carbon nanotube growth without any catalytic particles have also been demonstrated. These different growth systems are briefly examined in this article and serve to highlight the breadth of avenues available for carbon nanotube synthesis
Identifizierung von halbleitenden Bereichen in thermisch behandeltem monolagigem Oxo-funktionalisiertem Graphen
Synthesis of carbon nanotubes with and without catalyst particles
The initial development of carbon nanotube synthesis revolved heavily around the use of 3d valence transition metals such as Fe, Ni, and Co. More recently, noble metals (e.g. Au) and poor metals (e.g. In, Pb) have been shown to also yield carbon nanotubes. In addition, various ceramics and semiconductors can serve as catalytic particles suitable for tube formation and in some cases hybrid metal/metal oxide systems are possible. All-carbon systems for carbon nanotube growth without any catalytic particles have also been demonstrated. These different growth systems are briefly examined in this article and serve to highlight the breadth of avenues available for carbon nanotube synthesis