2D Oligosilyl Metal–Organic Frameworks as Multi‐state Switchable Materials

We report the synthesis of a set of 2D metal–organic frameworks (MOFs) constructed with organosilicon‐based linkers. These oligosilyl MOFs feature linear Si_nMe_2n(C₆H₄CO₂H)₂ ligands (lin‐Si_n, n=2, 4) connected by Cu paddlewheels. The stacking arrangement of the 2D sheets is dictated by van der Waals interactions and is tunable by solvent exchange, leading to reversible structural transformations between many crystalline and amorphous phases.     

Microfluidic assembly blocks

An assembly approach for microdevice construction using prefabricated microfluidic components is presented. Although microfluidic systems are convenient platforms for biological assays, their use in the life sciences is still limited mainly due to the high-level fabrication expertise required for construction. This approach involves prefabrication of individual microfluidic assembly blocks (MABs) in PDMS that can be readily assembled to form microfluidic systems. Non-expert users can assemble the blocks on glass slides to build their devices in minutes without any fabrication steps. In this paper, we describe the construction and assembly of the devices using the MAB methodology, and demonstrate common microfluidic applications including laminar flow development, valve control, and cell culture.     

Programmable fluidic production of microparticles with configurable anisotropy

We report a technique for continuous production of microparticles of variable size with new forms of anisotropy including alternating bond angles, configurable patchiness, and uniform roughness. The sequence and shape of the anisotropic particles are configured by exploiting a combination of confinement effects and microfluidics to pack precursor colloids with different properties into a narrow, terminal channel. The width and length of the channel relative to the particle size fully specify the configuration of the anisotropic particle that will be produced. The precursor spheres packed in the production zone are then permanently bonded into particles by thermal fusing. The flow in the production zone is reversed to release the particles for collection and use. Particles produced have linear chain structure with precisely configured, repeatable bond angles. With software programmable microfluidics, sequence and shape anisotropy are combined to yield synthesized homogeneous (type "A"), surfactantlike (type "A-B") or triblock (type "A-B-A") internal sequences in a single device. By controlling the dimensions of the microfluidic production zone, triangular prisms and particles with controlled roughness and patchiness are produced. The fabrication method is performed with precursors spheres with diameter as small as 3.0 microm.     

Fluorescent core-shell silica nanoparticles: towards "Lab on a Particle" architectures for nanobiotechnology

Novel nanoscale fluorescent materials are integral to the progress of emergent fields such as nanobiotechnology and facilitate new research in a variety of contexts. Sol-gel derived silica is an excellent host material for creating fluorescent nanoparticles by the inclusion of covalently-bound organic dyes. Significant enhancements in the brightness and stability of organic dye emission can be achieved for silica-based core-shell nanoparticle architectures at length scales down to tens of nanometers with narrow size distributions. This tutorial review will highlight these findings and describe the evolution of the fluorescent core-shell silica nanoparticle concept towards integration of multiple functionalities including mesoporosity, metal nanoshells and quantitative chemical sensing. These developments point towards the development of "lab on a particle" architectures with promising prospects for nanobiotechnology, drug development and beyond.     

Predictive modeling of positive mode IMS gas-phase ionization: is 2nd-order Møller-Plesset perturbation theory adequate?

Low level ab initio Quantum Chemistry (QC) is shown to be a promising technique for predicting the relative ordering of a wide variety of potential analyte, dopant, and interferent molecules, by their proton affinities (PA). Computed PAs, using a single level of chemical theory, are summarized for 53 compounds and when compared to literature reference data have a mean unsigned error of ∼9.5 kJ/mol. Where applicable, multiple conformations of the protonated species were explored. In these cases, the Boltzmann weighted PA is reported. Finally, examples are shown in which QC modeling is used to predict potential fragmentation products initiated by the positive mode ionization.     

Synthesis of glycopolymers via click reactions

This mini-review describes recent work in the field of glycopolymer synthesis, with a focus on methods that have employed “click chemistry” and controlled polymerization methodology. A variety of carbohydrates with clickable groups such as azide, alkyne, and thiol moieties provide new routes to glycopolymers. Several studies use copper catalyzed azide-alkyne cycloaddition (CuAAC) reactions to synthesize glycomonomers or to incorporate carbohydrates into a clickable polymeric backbone. Alternatively, there are many thiol based click reactions which provide metal-free synthesis, which are discussed in details.     

Quantitative impact of small angle forward scatter on whole blood oximetry using a Beer-Lambert absorbance model

It is well known that red blood cell scattering has an impact on whole blood oximetry as well as in vivo retinal oxygen saturation measurements. The goal of this study was to quantify the impact of small angle forward scatter on whole blood oximetry for scattering angles found in retinal oximetry light paths. Transmittance spectra of whole blood were measured in two different experimental setups: one that included small angle scatter in the transmitted signal and one that measured the transmitted signal only, at absorbance path lengths of 25, 50, 100, 250 and 500 μm. Oxygen saturation was determined by multiple linear regression in the 520-600 nm wavelength range and compared between path lengths and experimental setups. Mean calculated oxygen saturation differences between setups were greater than 10% at every absorbance path length. The deviations to the Beer-Lambert absorbance model had different spectral dependences between experimental setups, with the highest deviations found in the 520-540 nm range when scatter was added to the transmitted signal. These results are consistent with other models of forward scatter that predict different spectral dependences of the red blood cell scattering cross-section and haemoglobin extinction coefficients in this wavelength range.     

Self‐Assembly of Uranyl–Peroxide Nanocapsules in Basic Peroxidic Environments

A wide range of uranyl–peroxide nanocapsules have been synthesized using very simple reactants in basic media; however, little is known about the process to form these species. We have performed a density functional theory study of the speciation of the uranyl ions under different experimental conditions and explored the formation of dimeric species via a ligand exchange mechanism. We shed some light onto the importance of the excess of peroxide and alkali counterions as a thermodynamic driving force towards the formation of larger uranyl–peroxide species.     

Sorption of nonionic organic solutes from water to tetraalkylammonium bentonites: Mechanistic considerations and application of the Polanyi-Manes potential theory

This work describes the role of quaternary alkylammonium amendment length on sorption mechanisms of modified bentonites for four nonionic organic compounds; benzene, carbon tetrachloride, TCE, and 1,2-DCB. Tetramethyl to tetrabutyl alkyl amendments were studied and an important mechanistic shift occurred at the propyl chain length for all four solutes studied. Three- and four-carbon-chain functional groups on the ammonium cation resulted in a linear, rather than a curvilinear isotherm. The uptake on tetrapropyl and tetrabutylammonium clays was noncompetitive in binary systems and showed negligible sensitivity to temperature variations, indicating the linear isotherms describe a partitioning uptake mechanism for these organoclays. The adsorptive organoclays (tetramethyl and tetraethylammonium clays) were fit with the Dubinin-Radushkevich equation to investigate the application of the Polanyi-Manes potential theory to organoclay adsorption. It was found that TCE and carbon tetrachloride, with similar physical and chemical characteristics, behaved according to the Polanyi-Manes theory. Benzene showed an anomalously high adsorption volume limit, possibly due to dense packing in the adsorption space or chemisorption to the short chain alkyl groups.