(Invited) Modification and Analysis of Carbon Based Structures By Metal Nanoparticulate Ions

Abstract

Our collaborative work to create and soft land ionized gas phase single crystalline metal nanoparticulate ions onto substrates was motivated by Robert Hauge’s wish to produce templates for carbon nanotube carpet growth. Ionwerks created a machine to do this but, as is often the case, funding was found first for alternative applications. One such has been low energy (500 eV) injection of 8 nm silver nanoparticulate ions (AgNP-) into the near surface of bio-polymers. A uniform layer (70 e15 Ag atoms/cm2) of these implanted particles serve to assist the laser desorption of intact biomolecules from a brain tissue sample into the gas phase. Some of these desorbed molecules are ionized and can be transported into a mass spectrometer and uniquely identified by their exact mass to charge (m/z). By scanning a 50 micron focused laser across the surface of an AgNP implanted rat brain tissue sections, a complete mass spectrum can be acquired at each of several hundred thousand laser locations. Images of specific biomolecules can be derived from these spectra. Putative molecular biomarkers can then be identified by inter-comparing the numerous molecular images from each animal grouping within an animal study. Images from the same brain levels between injured (or diseased) and uninjured rats define histological micro domains in which elevated or decreased molecular ion intensities correlate with other measures of injury/disease state severity. Imaging of these biomarker ions is becoming useful in preclinical screening of drug candidates and should ultimately enter clinical settings. The AgNP enhanced mass spectral imaging has been also applied to the surface analysis of synthetic polymers, fullerenes, and nanotubes. A third application uses 30 keV, 15 nm AgNP ion impacts to form otherwise unattainable controlled nano-sized holes in graphene—especially “rebar” graphene. Alternatively, low energy soft landing at lower energy can form nanostructures upon the graphene which have implications for device formation. However, before departure, Bob made it clear that we needed to get back to carpet growth and other ideas which he outlined in extensive and explicit discussions—mostly at outdoor cafes and coffee shops. His dictates and imprimatur remain.