We describe a high-resolution, high-sensitivity negative-tone photoresist technique that relies on bottom-up preassembly of differential polymer components within cylindrical polymer brush architectures that are designed to align vertically on a substrate and allow for top-down single-molecule line-width imaging. By applying cylindrical diblock brush terpolymers (DBTs) with a high degree of control over the synthetic chemistry, we achieved large areas of vertical alignment of the polymers within thin films without the need for supramolecular assembly processes, as required for linear block copolymer lithography. The specially designed chemical compositions and tuned concentric and lengthwise dimensions of the DBTs enabled high-sensitivity electron-beam lithography of patterns with widths of only a few DBTs (sub-30 nm line-width resolution). The high sensitivity of the brush polymer resists further facilitated the generation of latent images without postexposure baking, providing a practical approach for controlling acid reaction/diffusion processes in photolithography.
We report on the co-emission of secondary ions and electrons resulting from 15 keV C60
+ and 30 keV C60
2+ impacts on targets of Al, Si, Au, CsI, glycine, and guanine. The study has been performed by the combination of an electron emission microscope and a time-of-flight (ToF) mass spectrometer. The electron emission occurs near the kinetic emission threshold, yet yields are notable (>3) for all investigated targets. A key observation for the projectile-target combinations studied is the absence of correlation between the electron emission and the number and type of co-emitted secondary ions for flat and homogeneous samples. This observation validates a novel concept of “positional mass spectrometry”. In this approach a surface is probed in the event-by-event bombardment detection mode. Impacts of an individual C60 projectile are localized via electron emission. The location combined with the corresponding secondary ion information allows to map the distribution of surface molecules. The unique feature of positional mass spectrometry is the ability to identify co-emitted ions from a single projectile impact. To test the concept an electron emission microscope has been combined with a ToF mass spectrometer; the device operates with synchronized detection of electrons and ions. The spatial resolution of the method depends on the kinetic energy and angular distribution of the secondary electrons and the aberrations of the electron optics. Initial tests of positional mass spectrometry showed a spatial resolution of 1.2 μm. Progress is anticipated with improvements in the electron optics used and application of projectiles generating more prolific electron emission.
The strategy of decorating antibiofouling hyperbranched fluoropolymer-poly(ethylene glycol) (HBFP-PEG) networks with a settlement sensory deterrent, noradrenaline (NA), and the results of biofouling assays are presented. This example of a dual-mode surface, which combines both passive and active modes of antibiofouling, works in synergy to improve the overall antibiofouling efficiency against barnacle cyprids. The HBFP-PEG polymer surface, prior to modification with NA, was analyzed by atomic force microscopy, and a significant distribution of topographical features was observed, with a nanoscopic roughness measurement of 110 ± 8 nm. NA attachment to the surface was probed by secondary ion mass spectrometry to quantify the extent of polymer chain-end substitution with NA, where a 3- to 4-fold increase in intensity for a fragment ion associated with NA was observed and 39% of the available sites for attachment were substituted. Cytoskeletal assays confirmed the activity of tethered NA on adhering oyster hemocytes. Settlement assays showed deterrence toward barnacle cyprid settlement, while not compromising the passive biofouling resistance of the surface. This robust strategy demonstrates a methodology for the incorporation of actively antibiofouling moieties onto a passively antibiofouling network.
This
study deals with assessing the homogeneity of a mixture of ultrasmall
nanoparticles differing only by their respective functionalization.
While measuring the relative abundance of nanoparticles with specific
functionalization is feasible with mass spectrometry, the determination
of mixed or segregated moieties is beyond current capabilities. Our
approach is based on SIMS with massive projectiles, specifically Au400
+4. A distinct
feature of bombardment with Au400
+4 is abundant emission of multiple secondary
ions from one projectile impact. Their analysis allows for examination
of coemitted and thus colocalized molecules within the emission area
of a single impact (∼10–15 nm in diameter). It is possible
to collect the mass spectrum from each projectile impact, which probes
individual nanodomains, allowing for examination of molecular homogeneity
at the nanoscale.
In the present work, the advantages of a new, 100kV platform equipped with a massive gold cluster source for the analysis of native biological surfaces are shown. Inspection of the molecular ion emission as a function of projectile size demonstrate a secondary ion yield increase of ~100x for 520 keV Au400+4 as compared to 130 keV Au3+1 and 43 keV C60. In particular, yields of tens of percent of molecular ions per projectile impact for the most abundant components can be observed with the 520 keV Au400+4 probe, respectively. A comparison between 520 keV Au400+4 ToF-SIMS and MALDI-MS data showed a similar pattern and similar relative intensities of lipids’ components across a rat brain sagittal section. The abundant secondary ion yields of analyte-specific ions makes 520 keV Au4004+ projectiles an attractive probe for sub-μm molecular mapping of native surfaces.
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