N-Heterocyclic carbene-based gold etchants.

N-Heterocyclic carbenes (NHCs) are an emerging alternative to thiols for the formation of stable self-assembled monolayers (SAMs) on gold. We examined several different species that have been used to produce NHC-based monolayers on gold, namely 1,3-diisopropyl-5-nitrobenzimidazolium iodide, 1,3-diisopropyl-5-nitrobenzimidazolium hydrogen carbonate, bis(1,3-diisopropyl-5-nitrobenzimidazolium)gold(I) iodide, and 1,3-diisopropyl-5-nitrobenzimidazole-2-ylidene. Contrary to expectation, solutions containing the first two species in tetrahydrofuran and dichloromethane caused visible loss of gold from thin-film-coated glass slides.

Targeting improved reproducibility in surface-enhanced Raman spectroscopy with planar substrates using 3D printed alignment holders.

Drop-casting is frequently used to deliver a sample for surface-enhanced Raman spectroscopy (SERS) and can result in inhomogeneous sample distribution during solvent evaporation. While soaking can provide better analyte homogeneity, it may require more sample than is available. Failure to optically sample analyte-rich substrate locations can compromise measurement outcomes.

Chemically tailoring nanopores for single-molecule sensing and glycomics.

A nanopore can be fairly-but uncharitably-described as simply a nanofluidic channel through a thin membrane. Even this simple structural description holds utility and underpins a range of applications. Yet significant excitement for nanopore science is more readily ignited by the role of nanopores as enabling tools for biomedical science.

An Open Source, Iterative Dual-Tree Wavelet Background Subtraction Method Extended from Automated Diffraction Pattern Analysis to Optical Spectroscopy.

Background subtraction is a general problem in spectroscopy often addressed with application-specific techniques, or methods that introduce a variety of implementation barriers such as having to specify peak-free regions of the spectrum. An iterative dual-tree complex wavelet transform-based background subtraction method (DTCWT-IA) was recently developed for the analysis of ultrafast electron diffraction patterns. The method was designed to require minimal user intervention, to support streamlined analysis of many diffraction patterns with complex overlapping peaks and time-varying backgrounds, and is implemented in an open-source computer program.

Chemically Functionalizing Controlled Dielectric Breakdown Silicon Nitride Nanopores by Direct Photohydrosilylation.

Nanopores are a prominent enabling tool for single-molecule applications such as DNA sequencing, protein profiling, and glycomics, and the construction of ionic circuit elements. Silicon nitride (SiN) is a leading scaffold for these <100 nm-diameter nanofluidic ion-conducting channels, but frequently challenging surface chemistry remains an obstacle to their use. We functionalized more than 100 SiN nanopores with different surface terminations-acidic (Si-R-OH, Si-R-COH), basic (Si-R-NH), and nonionizable (Si-R-CH(CF))-to chemically tune the nanopore size, surface charge polarity, and subsequent chemical reactivity and to change their conductance by changes of solution pH.

Surveying silicon nitride nanopores for glycomics and heparin quality assurance.

Polysaccharides have key biological functions and can be harnessed for therapeutic roles, such as the anticoagulant heparin. Their complexity-e.g.