Molecular depth profiling of organic and biological materials

Atomic depth profiling using secondary ion mass spectrometry, SIMS, is common in the field micro-electronics; however, the generation of molecular information as a function of sample depth is difficult due to the accumulation of damage both on and beneath the sample surface. The introduction of polyatomic ion beams such as SF₅ and C₆₀ have raised the possibility of overcoming this problem as they deposit the majority of their energy in the upper surface of the sample resulting in increased sputter yields but with a complimentary reduction in sub-surface damage accumulation. In this paper we report the depth profile analysis of the bio-polymer polycaprolactone, PCL, using the polyatomic ions Au₃⁺ and C₆₀⁺ and the monoatomic Au+. Results are compared to recent analysis of a similar sample using . depth profiling of cellulose is also demonstrated, an experiment that has been reported as unsuccessful when attempted with implications for biological analysis are discussed.

Molecular gels for controlled formation of micro-/nano-structures

The preparation of nano structured materials such as nanoparticles, nanofiber and nanowires have been a focus of research in the last two decades. Due to their large surface-to-volume ration and superior properties compared to the conventional macroscopic materials, these materials promise to revolutionize many fields such as electronics, catalysis, and biomedicine. Hence, controlling the growth of these nanostructures has been a global interest. Although controlling the formation of macroscopically sized inorganic materials can be easily achieved, it is a challenge if the size of a material is reduced to a micrometer or nanometer scale. Synthesis of structures using organic templates has been demonstrated to be a simple and convenient approach, since the organic matter can be easily removed by calcination or suitable solvents. These organic templates include colloidal particles and fibers of polymers, aggregates of surfactants, carbon materials such as carbon nanotubes, organic crystals and fibers in small-molecule gels (SMGs) and polymer gels.

Shrinkage induced stretchable micro-wrinkled reduced graphene oxide composite with recoverable conductivity

A novel thermo-mechanical shrinking method is reported to fabricate a three dimensional (3D) stretchable and highly conductive micro-wrinkled reduced graphene oxide (MWrGO) supported on an elastic polydimethylsiloxane (PDMS) substrates. This 3D rGO architecture not only increases the specific area for more electrons to pass through but also bestows stretchability to the conductive pathway. The structural change of micro-wrinkles has been monitored by an in situ straining microscopy. The electrical conductivity of the samples remained fairly constant and stayed above 25 S/m under low deformation (no more than 30% strain) for up to 500 mechanical stretching-release cycles. Additionally, the MWrGO/PDMS composite can be stretched bi-axially because the shrinking process itself is isotropic. This MWrGO based stretchable composite with stable electrical properties and long life span could form a new platform of stretchable electronics.