Homochiral or Heterochiral: A Systematic Study of Threonine Clusters Using a FT ICR Mass Spectrometer

The strong chiral preferences of some magic clusters of amino acids have attracted continually increasing interests due to their unique structures, properties and possible roles in homochirogenesis. However, how chirality can influence the generation and stability of cluster ions in a wild range of cluster sizes is still unknown for most amino acids. In this study, the preference for threonine clusters to form homochiral and heterochiral complex ions has been investigated by electrospray ionization (ESI) mass spectrometry. Abundant cluster [Thrn+mH]m+ ions (7 ≤ n ≤ 78, 1 ≤ m ≤ 5) have been observed for both samples of enantiopure (100% L) and racemic (50:50 L:D) threonine solutions. Further analyses of the spectra show that the [Thr14+2H]2+ ion is characterized by its most outstanding homochiral preference, and [Thr7+H]+ and [Thr8+H]+ ions also clearly exhibit their homochiral preferences. Although most of the triply charged clusters (20 ≤ n ≤ 36) are characterized by heterochiral preferences, the quadruply charged [Thrn+4H]4+ ions (40 ≤ n ≤ 59) have no obvious chiral preference in general. On the other hand, a weak homochiral preference exists for most of the quintuply charged ions observed in the experiment.

Crosslinking Multilayer Graphene by Gas Cluster Ion Bombardment

In this paper, we demonstrate a new, highly efficient method of crosslinking multilayer graphene, and create nanopores in it by its irradiation with low-energy argon cluster ions. Irradiation was performed by argon cluster ions with an acceleration energy E ≈ 30 keV, and total fluence of argon cluster ions ranging from 1 × 109 to 1 × 1014 ions/cm2. The results of the bombardment were observed by the direct examination of traces of argon-cluster penetration in multilayer graphene, using high-resolution transmission electron microscopy. Further image processing revealed an average pore diameter of approximately 3 nm, with the predominant size corresponding to 2 nm. We anticipate that a controlled cross-linking process in multilayer graphene can be achieved by appropriately varying irradiation energy, dose, and type of clusters. We believe that this method is very promising for modulating the properties of multilayer graphene, and opens new possibilities for creating three-dimensional nanomaterials.

SPUTTERING OF GOLD AND COPPER SURFACES UNDER LOW ENERGY CESIUM IONS

To use gold and copper ions for ion implantation through 1-MV pelletron accelerator, gold and copper targets were bombarded with low energy cesium ions applying source of negative ions by cesium sputtering (SNICS). This work aims to investigate the cluster dynamics of these noble metals in a low energy range so that optimized data can be obtained for the use of these cluster ions in ion implantation. Negative ions including monomers and clusters of both metals were detected which were mass analyzed. Cu clusters up to Cu[Formula: see text] and gold clusters up to Au[Formula: see text] were emitted. The minimum energy of cesium ions to produce enough cluster ions so that they could be detected by a mass analyzer has been determined. The data was analyzed to measure sputtering yield, total sputtering yield and normalized number density of different sputtered species. In this energy range, the sputtering behaviors of Cu remain almost constant but in the case of Au there is a slight increase in cluster sputtering probability with an increase in incident ion energy. The sputtering yield of clusters decreases according to the power-law, i.e. [Formula: see text]. Power law exponent in the case of copper has an average value of [Formula: see text] whereas exponent in the case of gold clusters changes from 3.5 to 6.

Laser desorption/ionization time-of-flight mass spectrometry of yttrium(III) chloride

Due to the increased use of yttrium in agriculture and industry, there is a growing interest in the impact of yttrium on the environment and human health. Developing novel procedures to detect and quantify species of yttrium represents an important task. In this work, we apply laser desorption/ionization-mass spectrometry (LDI-MS) to detect cluster ions of the solution of yttrium(III) chloride (YCl3) at different pH values. The density functional theory (DFT) calculations were used to reveal the energetically most favored structures of the anions and cations chosen from the LDI-MS results. Examination of the positive and negative mode LDI mass spectra of YCl3 showed the presence of the heterogeneous mononuclear and polynuclear clusters, such as [YCl(OH) (H2O)3][Formula: see text], [Y2(H2O)][Formula: see text], [Y4H2(H2O)4][Formula: see text], and [Y5O4H3][Formula: see text] (at pH 2 and 5) and [Y2Cl2(H2O)2][Formula: see text], [Y2O5(HCl)(OH)][Formula: see text], and [Y3OH3(OH)2(H2O)][Formula: see text] (at pH 2, 5, and 10). The variation in the pH solution of YCl3 slightly affects the LDI mass spectrum of these yttrium clusters. It has only been noticed that the [Y4H2(H2O)4][Formula: see text] cluster ions were not detected at pH 10. These results can become a guide in the detection of yttrium chloride by LDI-MS in real samples in different fields (ecological, food, and human).

Study of radial motion phase advance during motion excitations in a Penning trap and accuracy of JYFLTRAP mass spectrometer

Phase-imaging ion-cyclotron-resonance technique has been implemented at the Penning-trap mass spectrometer JYFLTRAP and is routinely employed for mass measurements of stable and short-lived nuclides produced at IGISOL facility. Systematic uncertainties that impose limitations on the accuracy of measurements are discussed. It was found out that the phase evolution of the radial motion of ions in a Penning trap during the application of radio-frequency fields leads to a systematic cyclotron frequency shift when more than one ion species is present in the trap during the cyclotron frequency measurement. An analytic expression was derived to correctly account for the shift. Cross-reference mass measurements with carbon-cluster ions have been performed providing the mass-dependent and residual uncertainties.