Chemical design of nanoparticle probes for high-performance magnetic resonance imaging

Synthetic magnetic nanoparticles (MNPs) are emerging as versatile probes in biomedical applications, especially in the area of magnetic resonance imaging (MRI). Their size, which is comparable to biological functional units, and their unique magnetic properties allow their utilization as molecular imaging probes. Herein, we present an overview of recent breakthroughs in the development of new synthetic MNP probes with which the sensitive and target-specific observation of biological events at the molecular and cellular levels is possible.     

Decomposition of hexamethyldisilane on a hot tungsten filament and gas-phase reactions in a hot-wire chemical vapor deposition reactor

To study the effect of an Si-Si bond on gas-phase reaction chemistry in the hot-wire chemical vapor deposition (HWCVD) process with a single source alkylsilane molecule, soft ionization with a vacuum ultraviolet wavelength of 118 nm was used with time-of-flight mass spectrometry to examine the products from the primary decomposition of hexamethyldisilane (HMDS) on a heated tungsten (W) filament and from secondary gas-phase reactions in a HWCVD reactor. It is found that both Si-Si and Si-C bonds break when HMDS decomposes on the W filament. The dominance of the breakage of Si-Si over Si-C bond has been demonstrated. In the reactor, the abstraction of methyl and H atom, respectively, from the abundant HMDS molecules by the dominant primary trimethylsilyl radicals produces tetramethylsilane (TMS) and trimethylsilane (TriMS). Along with TMS and TriMS, various other alkyl-substituted silanes (m/z = 160, 204, 262) and silyl-substituted alkanes (m/z = 218, 276, 290) are also formed from radical combination reactions. With HMDS, an increasing number of Si-Si bonds are found in the gas-phase reaction products aside from the Si-C bond which has been shown to be the major bond connection in the products when TMS is used in the same reactor. Three methyl-substituted 1,3-disilacyclobutane species (m/z = 116, 130, 144) are present in the reactor with HMDS, suggesting a more active involvement from the reactive silene intermediates.     

Nanoparticle assisted magnetic resonance imaging of the early reversible stages of amyloid beta self-assembly

Co@Pt-Au nanoparticles, which have enhanced magnetism and high stability in aqueous media, are utilized in conjunction with MRI to monitor the structural evolution of Abeta assemblies, especially Abeta protofibrils in the early reversible stages.     

Statistical mechanics of molecular adsorption: effects of adsorbate interaction on isotherms

We investigate a simple, exactly solvable model for interacting adsorbates. From the model study, we find that (1-theta)(-1) as a function of density of molecules in bulk media can have a positive curvature only in the presence of attractive interaction between adsorbed molecules. We propose a novel experimental observable, chi. Positive chi is the sufficient condition for the presence of attractive interactions between adsorbate molecules.     

Surface-Modified Carbon Materials for CO2 Electroreduction

The electrochemical reduction of CO₂ to produce sustainable fuels and chemicals has attracted great attention in recent years. It is shown that surface-modified carbons catalyze the CO₂RR. This study reports a strategy to modify the surface of commercially available carbon materials by adding oxygen and nitrogen surface groups without modifying its graphitic structure. Clear differences in CO₂RR activity, selectivity and the turnover frequency between the surface-modified carbons were observed, and these differences were ascribed to the nature of the surface groups chemistry and the point of zero charge (PZC). The results show that nitrogen-containing surface groups are highly selective towards the formation of CO from the electroreduction of CO₂ in comparison with the oxygen-containing surface groups, and the carbon without surface groups. This demonstrates that the selectivity of carbon for CO₂RR can be rationally tuned by simply altering the surface chemistry via surface functionalization.     

Tuning of fluorescence properties of aminoterpyridine fluorophores by N-substitution

Several N-alkyl and N-phenyl derivatives of 6-amino- () and 6,6'-diamino-2,2':6',2'-terpyridine () were synthesized, and their fluorescence properties were studied. A successive red-shift was observed as the number of the N-substituted groups increased. It was also shown that the susceptivity of the fluorophores to a solvent varied considerably according to the mode of the N-substitution. While the monoamino-tpys (tpy: 2,2':6',2'-terpyridine) suffered almost complete quenching of their fluorescence in ethanol, the fully N-alkylated diamino-tpys and retained their fluorescence. The results show that N-substitution is a useful way to tune both the radiation energy and solvent susceptivity of the fluorescence of the amino-tpys.