Laser desorption-membrane introduction mass spectrometry.

In this paper we describe the first use of laser desorption in conjunction with membrane introduction mass spectrometry (MIMS). In this technique, a low-powered carbon dioxide laser is used to irradiate the low-pressure (vacuum) side of a silicone membrane during a typical MIMS analysis of an aqueous solution. The absorption of laser energy results in direct membrane heating and rapid desorption of permeate molecules. This improves both the sensitivity and response times of MIMS when analyzing compounds having high molecular weight and low volatility. Two simple interfaces are described for performing laser desorption inside and outside the vacuum manifold of a GCQ ion trap mass spectrometer. Together with flow injection (FI) sample introduction, we demonstrate direct on-line monitoring of aqueous solutions of high boiling point (200-530 °C) polynuclear aromatic hydrocarbons such as naphthalene, anthracene, pyrene, benzo[b]fluoranthene, and indeno[123-cd]pyrene.

Large odd-numbered carbon clusters from fullerene-ozone reactions.

The odd-numbered carbon clusters C(119), C(129), and C(139) have been observed in the mass spectra of toluene extracts of fullerene soots and of the products of ozone-fullerene reactions. Specifically, ozone-C(60) reactions yield C(119), ozone-C(70) reactions yield C(139), and ozone-(C(60)/C(70)) reactions produce C(119), C(129), and C(139). These unexpected species correspond to dimers of C(60), C(60)/C(70), and C(70), respectively, less one carbon atom, and are stable gas-phase ions with behavior similar to that of fullerenes. The results suggest a new route to functionalization and derivatization of fullerenes through controlled ozone-catalyzed cage-opening reactions.

Cyclocarbon coalescence: mechanisms for tailor-made fullerene formation.

The availability of macroscopic quantities of fullerenes has resulted in a vast number of physical and chemical studies of these new materials. However, the mechanisms that lead to the formation of these spherical carbon allotropes are not well understood. Mass spectral evidence has been obtained for the size-selective growth of fullerenes through the coalescence of cyclo[n] carbons, molecular carbon allotropes consisting of monocyclic rings with n carbon atoms. Whereas coalescence of cyclo[30]carbon (cyclo-C(30)) produces predominantly buckminsterfullerene (C(60)), the smaller rings cyclo-C(l8) and cyclo-C(24) preferentially produce fullerene C(70) through distinct intermediates. The present studies not only provide new insights into fullerene formation mechanisms but also raise the possibility of tailoring the size distributions of fullerenes by variation of the appropriate properties of the precursors.

Mass spectrometry and fullerenes.

This article presents, from amass spectrometry perspective, an historical account of research on gas-phase carbon clusters, which has led to the discovery of another form of carbon, fullerenes. In addition, more recent mass spectrometric studies on analysis of fullerene derivatives and synthesis of doped fullerenes are described. The early, strong evidence for certain "magic number" carbon clusters, most notably C60 (buckminsterfullerene), was obtained largely from mass spectrometric experiments. These studies led to the controversial postulation of the soccerball structure for C60, which provoked increased experimental and theoretical efforts. This research eventually resulted in the discovery of a simple method by which large quantities of fullerenes can be produced. The availability of these new, all-carbon molecules has motivated a broad range of synthetic and characterization studies that are expanding at a frenetic pace. Mass spectrometry not only played a critical role in the discovery of fullerenes but also now is crucial for determination of the unusual chemical and physical properties of fullerenes and fullerene-based materials.