Nanoscale Science and Technology at Los Alamos National Laboratory

Research in the emerging field of nanoscale science and technology has grown steadily at Los Alamos National Laboratory since 1990. This article summarizes some of this work, examining research highlights within the seven key categories of nanoscience in which Los Alamos has ongoing projects, capabilities, and facilities: (1) Materials and chemistry, (2) Theory and modeling, (3) Bioscience, (4) Investigative tools and facilities, (5) Sensors and devices, (6) Synthesis and fabrication, and (7) Education and outreach. Future research horizons are indicated throughout while institutional strategies for advancing nanoscale science are summarized at the end.     

Nitrogen isotope enrichment via infrared laser induced isomerization of methyl and ethyl isocyanide

Methyl and ethyl isocyanide undergo isomerization to the corresponding nitriles when irradiated with the focused output of a CO₂ TEA laser. This process is shown to be isotopically selective for nitrogen isotopes when operating pressures are on the order of 1 to 2 torr. At higher pressures thermal isomerization becomes dominant.     

The molecular Zeeman effect in HCP,HCN, and HCCBr and a comparison with similar molecules

The molecular Zeeman effect has been observed in the J = 0 → 1 ΔM = 0, and ± 1 transitions in H¹²CP, D¹²CP, H¹²C¹⁵N, H¹²C¹²C⁷⁹Br, and H¹²C¹²C⁸¹ Br giving the molecular g-values, magnetic susceptibility anisotropies, and corresponding molecular quadrupole moments. The results are g_⊥(HCP) = ?0.0430 ± 0.0010, g_⊥(DCP) = ?0.0353 ± 0.0010, x_⊥ - x_| = (8.4 ± 0.9) × 10^?6 erg/G² mole and Q_|(HCP) = (4.4 ± 1.2) × 10^?26 esu; g_⊥(HC¹⁵N) = ?0.0904 ± 0.0003, x_⊥ - x_| = (7.2 ± 0.4) × 10^?6 erg/G² mole, and Q_|(HC¹⁵N) = (3.1 ± 0.6) × 10^?26 esu; g_⊥(HCC⁷⁹Br) = ?0.00395 ± 0.00032, g_⊥(HCC⁸¹Br) = ?0.00388 ± 0.00014, x_⊥ - x_| = (9.5 ± 0.9) × 10^?6 erg/G² mole, and Q_| = (8.5 ± 1.1) × 10^?26 esu. The results in HCN agree very well with an earlier prediction of the magnetic properties. The new results presented here are compared to other members in the acetylene and cyanide series of molecules and we conclude that the sign of the g-value in acetylene should be positive.The deuterium nuclear quadrupole coupling constant was also determined in DCP to be x_D = 233 ± 40 kHz.     

Confocal microscopy of whole mount embryonic cartilage: Intracellular localization of F-actin, chick prolyl hydroxylase and type II collagen mRNA

We show that whole mount preparations of embryonic chick sterna can be analyzed with confocal laser scanning microscopy (CLSM). This technique replaces the traditional sectioning of cartilage or culturing of chondrocytes. Whole ‘chunks’ of cartilage can be stained with dyes, used for immunohistochemistry or in situ hybridization. Although other stains have been used, the stains presented include phalloidin and propidium iodide which stain filamentous actin (F-actin) and the DNA and RNA of cells, respectively. Collagen secreting endoplasmic reticulum (ER) was localized with a primary antibody to chick prolyl hydroxylase (CPH) that was detected with a secondary antibody conjugated to FITC. The intracellular localization of type II collagen mRNA was analyzed using in situ hybridization. The cDNA probe specific for the C-propeptide region of the 1 type (II) collagen mRNA was nick translated and labeled with biotin-16-dUTP. Biotin labeled probes were visualized with avidin-FITC. Depending on the intensity of the stain, we were able to analyze approximately 3–10 layers of chondrocytes. Stains penetrated into the cartilage better than antibodies and biotin-avidin labeled cDNA probes. The F-actin was located as bands of filaments in the superficial layers of the cartilage and was associated with the membranes that marked cell boundaries as deep as 10 layers of chondrocytes. The ER stained with anti-chick prolyl hydroxylase was prominent in perinuclear regions of the cells, but the antibody was only able to penetrate 4–5 cell layers. Single label in situ hybridization studies show that chondrocytes are positive for type II collagen mRNA. Similar to the immunohistochemistry, in situ hybridization probes were only able to penetrate 4–5 cell layers. The type II collagen mRNA appeared perinuclear in the chondrocytes, similar to the ER staining pattern.     

Infrared multiphoton dissociation of DN3 and HN3: Formation and reaction of electronically excited ND

Chemiluminescence is observed from DN₃ at pressures below 100 mtorr following irradiation with the focused output of a CO₂ TEA laser. Emission is attributed to ND₂(²A_I) formed in the reaction ND(a¹Δ) + DN₃ → ND₂ (²A₁) + N₃. The ND(a¹Δ) is produced in the primary photolysis. Time resolved studies of the fluorescence permit determination of the rate constant for the chemiluminescent reaction (2.09 ± 0.31 μs^?1 torr^?1). Multiphoton dissociation of HN₃ by use of a laser wavelength coincident with a hot band absorption is also demonstrated.     

Infrared multiphoton dissociation of methyl nitrite

Methyl nitrite undergoes dissociation when irradiated with the focused output of a pulsed CO₂ TEA laser. Time resolved infrared emission is observed and attributed to vibrationally excited formaldehyde and methanol. These species are produced via reactions of methoxy radicals formed in the primary dissociation. Other products formed are NO and N₂O.