Surface-enhanced Raman scattering on silver nanostructured films prepared by spray-deposition

Silver nanostructured films were directly prepared by spray deposition of preformed polyol-based Ag-PVP nanoparticles. These homogeneous films of high optical quality were tested as SERS-active substrates. Laser excitation at 514.5 nm within the red part of the plasmon band leads to intense and reproducible SERS spectra of acridine, used as the probe molecule. From SERS measurements at different pH values, it was possible to determine the apparent pK(a) of acridine and to obtain specific surface properties of the film. Finally, these SERS titrations along with enhancement factor estimates allowed us to further depict the nature of the films.     

Data-Dependent Acquisition with Precursor Coisolation Improves Proteome Coverage and Measurement Throughput for Label-Free Single-Cell Proteomics**

We combined efficient sample preparation and ultra-low-flow liquid chromatography with a newly developed data acquisition and analysis scheme termed wide window acquisition (WWA) to quantify >3,000 proteins from single cells in rapid label-free analyses. WWA employs large isolation windows to intentionally co-isolate and co-fragment adjacent precursors along with the selected precursor. Optimized WWA increased the number of MS2-identified proteins by ≈40 % relative to standard data-dependent acquisition. For a 40-min LC gradient operated at ≈15 nL/min, we identified an average of 3,524 proteins per single-cell-sized aliquot of protein digest. Reducing the active gradient to 20 min resulted in a modest 10 % decrease in proteome coverage. Using this platform, we compared protein expression between single HeLa cells having an essential autophagy gene, atg9a, knocked out, with their isogenic WT parental line. Similar proteome coverage was observed, and 268 proteins were significantly up- or downregulated. Protein upregulation primarily related to innate immunity, vesicle trafficking and protein degradation.     

Turning on the Antimicrobial Activity of Gold Nanoclusters Against Multidrug-Resistant Bacteria**

In this work, we show that the addition of thiourea (TU) initiated broad-spectrum antimicrobial activity of otherwise inactive D-maltose-capped gold nanoclusters (AuNC-Mal). For example, AuNC-Mal/TU was effective against multidrug-resistant Pseudomonas aeruginosa with a minimum inhibitory concentration (MIC) of 1 μg mL⁻¹ (2.5 μM [Au]) while having 30–60 times lower in vitro cytotoxicity against mammalian cells. The reaction of AuNC-Mal and TU generated the antimicrobial species of [Au(TU)₂]⁺ and smaller AuNCs. TU increased the accumulation of Au in bacteria and helped maintain the oxidation state as Au^I (vs. Au^III). The modes of action included the inhibition of thioredoxin reductase, interference with the Cu^I regulation and depletion of ATP. Moreover, the antimicrobial activity did not change in the presence of colistin or carbonyl cyanide 3-chlorophenylhydrazone, suggesting that AuNC-Mal/TU was indifferent to the outer membrane barrier and to bacterial efflux pumps.     

Photochemical behavior of inorganic and organic selenium compounds in various aqueous solutions

Selenium possesses interesting chemical, biochemical and geochemical behaviors. However, studies of its photochemical properties in aqueous systems are scarce. A better understanding of these phenomena is of great importance for further application of such properties to selenium speciation. In this work, the photochemical behavior of selenium and some of its organic compounds have been systematically studied in various aqueous matrices under UV irradiation at 300 nm. It was observed that the photochemical oxidation rate of Se(IV) to Se(VI) was greatly enhanced in the presence of HN0₃ at ≥1 × 10⁻³ M, but not by NaNO₃. However this photo-oxidation could be inhibited by the presence of Cl⁻. Under UV irradiation, organoselenium compounds went through two successive photochemical reactions in pure water: a direct photolysis (photo-cleavage) followed by a photo-oxidation to form Se(VI). These two steps could also be greatly accelerated in presence of NO₃⁻ although the second step required an acidic condition. The photo cleavage rates varied from one organic compound to another and 10-fold differences were observed. Similarly to Se(IV), the further oxidation to Se(VI) could be prevented by Cl⁻ for all studied organoselenium compounds. Detailed reaction mechanisms involving OH radicals are proposed to explain Se photochemical behaviors in different matrices.     

Theoretical study of modes of adsorption of water dimer on H-ZSM-5 and H-Faujasite zeolites

Modes of adsorption of water dimer on H-ZSM-5 and H-Faujasite (H-FAU) zeolites have been investigated by a quantum embedded cluster approach, using the hybrid B3LYP density functional theory. The results indicate that there are two possible adsorption pathways, namely the stepwise process where only one water binds strongly to the (-O)3-Al-O(H) tetrahedral unit while the other weakly binds to the zeolite framework and the concerted process where both water molecules form a large ring of hydrogen-bonding network with the Br?nsted proton and an oxygen framework. With inclusion of the effects of the Madelung potential from the extended zeolite framework, for adsorption on H-ZSM-5 zeolite, both the neutral and ion-pair complexes exist with adsorption energies of -15.13 and -14.73 kcal/mol, respectively. For adsorption on the H-FAU, only the ion-pair complex exists with the adsorption energy of -14.63 kcal/mol. Our results indicate that adsorption properties depend not only on the acidity of the Br?nsted acidic site but also on the topology of the zeolite framework, such as on the spatial confinement effects which lead to very different adsorption structures for the ion-pair complexes in H-ZSM-5 and H-FAU, even though their adsorption energies are quite similar. Our calculated vibrational spectra for these ion-pair complexes support previous experimental IR interpretations.     

Wavelength Orthogonal Photodynamic Networks

The ability of light to remotely control the properties of soft matter materials in a dynamic fashion has fascinated material scientists and photochemists for decades. However, only recently has our ability to map photochemical reactivity in a finely wavelength resolved fashion allowed for different colors of light to independently control the material properties of polymer networks with high precision, driven by monochromatic irradiation enabling orthogonal reaction control. The current concept article highlights the progress in visible light-induced photochemistry and explores how it has enabled the design of polymer networks with dynamically adjustable properties. We will explore current applications ranging from dynamic hydrogel design to the light-driven adaptation of 3D printed structures on the macro- and micro-scale. While the alternation of mechanical properties via remote control is largely reality for soft matter materials, we herein propose the next frontiers for adaptive properties, including remote switching between conductive and non-conductive properties, hydrophobic and hydrophilic surfaces, fluorescent or non-fluorescent, and cell adhesive vs. cell repellent properties.     

Synthesis of allyl end‐block functionalized poly(ε‐caprolactone)s and their facile post‐functionalization via thiol–ene reaction

A simple and facile strategy for the functionalization of commercial poly(ε‐caprolactone) diols (PCLs) with pendant functionalities at the polymer chain termini is described. Well‐defined allyl‐functionalized PCLs with varying numbers of allyl end‐block side‐groups were synthesized by cationic ring‐opening polymerization of allyl glycidyl ether using PCL diols as macroinitiators. Further functionalization of the allyl‐functionalized PCLs was realized via the UV‐initiated radical addition of a furan‐functionalized thiol to the pendant allyl functional groups, showing the suitability for post‐modification of the PCL materials. Changes in polymer structure as a result of varying the number of pendant functional units at the PCL chain termini were demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 928–939