Spatially resolved chemical imaging is achieved by combining a fiber-optic scanning probe microscope with laser-induced breakdown spectroscopy in a single instrument, TOPOLIBS. Elemental composition of surfaces can be mapped and correlated with topographical data. The experiment is conducted in air with minimal sample preparation. In a typical experiment, surface topography is analyzed by scanning a sharp fiber-optic probe across the sample using shear force feedback. The probe is then positioned over a feature of interest and pulsed radiation is delivered to the surface using a nitrogen laser. The pulse vaporizes material from the surface and generates a localized plasma plume. Optical emission from the plume is analyzed with a compact UV/visible spectrometer. Ablation crater size is controlled by the amount of laser power coupled into the probe. Sampling areas with submicrometer dimensions are achieved by using reduced laser power.
Typical infrared transmitting fibers comprise a chalcogenide core surrounded by a sulfur-selenide cladding, which is in turn coated with a polymer such as polyamide. For use in a near-field scanning infrared microscope ͑NSIM͒, such infrared-transmitting fibers must be tapered to a sharp point. Sharper points allow smaller apertures, which allow higher resolution. The light throughput of the probe depends on the length of the taper region: the longer the taper length, the further the infrared radiation must propagate through a waveguide smaller than its wavelength. Thus, shorter taper lengths should give higher light throughput. We describe a method for etching chalcogenide fibers to submicron points by simple chemical means. Methods are described for removal of the polyamide coating, stripping of the SSe cladding surrounding the core, and etching the chalcogenide fiber core to a sharp point. Removal of the polyamide coating is most easily accomplished by dissolution in 4-Chloro-1-butanol. The SSe cladding is removed by soaking the fiber in 0.1 M NaOH overnight. The chalcogenide core is tapered to a sharp point by immersion in a two-phase etching system, where the top phase is an inert organic solvent, and the bottom phase is a strong oxidant. Fibers both with and without cladding have been tapered. The resulting fibers have a taper length on the order of the core diameter, and terminate with a submicron end radius of curvature. The potential for use in a NSIM, as well as other uses, is discussed.
Water clusters of salen [N,N‘-ethylenebis(salicylideneaminato)] transition metal complexes [(salen)M,
M = Cr3+, Mn3+, Co3+] formed by electrospray source have been investigated using a Fourier transform ion
cyclotron resonance (FT-ICR) mass spectrometer. Kinetics of water evaporation from the cluster ions is observed
to be highly dependent on the central metal ion. For example, the evaporation rate of water from solvated
salen chromium ion ([SCr + nH2O]+) is significantly slower than that from solvated salen manganese
([SMn + nH2O]+) and solvated salen cobalt ([SCo + nH2O]+) ions. Furthermore, the clusters of salen chromium
ions with two waters attached exhibit special stability, indicated by their prominence in the overall cluster
distribution. In contrast, no specific solvation is observed for the manganese and cobalt complexes. The lability
observed for the hydrated salen cobalt complex suggests that the high-spin state is likely to be involved in the
evaporation process. These results are in accordance with observations in solution-phase chemistry and can be
explained by ligand field theory.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.