The striking influence of SWNT-COOH on self-assembled gelation

A miniscule amount of f-SWNTs remarkably improved (~17-fold) the gelation efficiency of amphiphilic molecules by triggering the formation of interconnecting self-assembled fibrillar networks (SAFIN) in supramolecular gelation.     

One-pot thioetherification of aryl halides with thiourea and benzyl bromide in water catalyzed by Cu-grafted furfural imine-functionalized mesoporous SBA-15

Surface functionalization of SBA-15 followed by its reaction with Cu(OAc)(2) has been carried out to develop a new Cu-grafted functionalized mesoporous material, which catalyzes one-pot three component coupling of different aryl halides with thiourea and benzyl bromide in aqueous medium to produce aryl thioethers in very good yields (80-88%).     

Multielectron Redox Chemistry of a Neutral,NIR‐Active,Indigo‐Pillared ReI‐Based Triangular Metalloprism

Self‐assembled, hexarhenium(I), triangular metalloprism compound [{(CO)₃Re(μ‐ 2 )Re(CO)₃}₃(μ₃‐ 1 )₂] ( 3 ) featuring three bis‐chelating pillarlike indigo dianions (μ‐ 2 ), each of which connects two fac‐Re(CO)₃ cores, which are interconnected by a tritopic N donor, that is, a 2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine (μ₃‐ 1 , tPyTz) ligand, has been synthesized in high yield and characterized. Metalloprism 3 exhibits a strong absorption in the near‐infrared (NIR) region. The reversible, multielectron redox properties of the electrogenerated 3 ⁿ species, where n=3+, 0, 3?, 4?, 5?, 8?, in the visible and especially in the NIR region were investigated in THF solution by cyclic voltammetry (CV), chronocoulometry, EPR spectroscopy, and thin‐layer UV/Vis/NIR spectroelectrochemistry (SEC). Stepwise, site‐specific electrochemical reductions lead to the formation of a series of highly stable ion (radical) species in which electrons associated with μ‐ 2 or μ₃‐ 1 components of the molecule can be clearly distinguished. An EPR investigation revealed interaction of unpaired electrons with the metal nuclei (^185,187Re, I=5/2) in the reduced intermediates. The framework has C₂ symmetry, and accidental degeneracies suffice. Detailed theoretical calculations by structure‐based DFT confirm that the triply degenerate HOMO has ≥70 % indigo character with a sizable dπ‐Re character, while the LUMO is dominated by the triply degenerate indigo ligands, and the LUMO+1 by doubly degenerate tPyTz ligands. A comparison of 3 and previously reported 2,2′‐bis‐benzimidazolate‐ (BiBzlm) or alkoxy‐pillared Re^I metalloprisms indicates a very low switching potential with a potential window of less than 1 V and reversibly accessible optical properties with higher stability of the intermediates. The properties exhibited by 3 appear to be due to the slight tuning of the bridging ligand from N,N^? to N,O^?.     

Photophysical and photodynamical study of fluoroquinolone drug molecule in bile salt aggregates

Photophysical properties of two widely used antibiotic fluoroquinolone drugs, namely Norfloxacin (NOR) and Ofloxacin (OFL) have been investigated in biomimicking environments formed by bile salts. Experimental results demonstrate that photophysical enhancement and fall of a particular prototropic species are sensitive to the excitation wavelength in bile salt aggregates. Excitation at shorter wavelengths reveals quenching of fluorescence of these fluoroquinolone with addition of sodium deoxycholate (NaDC), sodium taurocholate (NaTC) and sodium glycodeoxycholate (NaGDC). On the contrary, we observe a steady increase in the fluorescence intensity with a continuous redshift upon excitation at longer wavelength. The experimental results were rationalized in terms of the fact that, neutral and zwitterionic species of fluoroquinolone molecules in bile salt aggregates are selectively excited at shorter wavelength while the cationic form of fluoroquinolone molecules are excited at longer wavelength. The excess hydronium ions in the hydrophilic surface of bile salt aggregates convert the neutral species of NOR and OFL into cationic species causing an enhancement in the emission intensity. We found that NaGDC and NaTC because of the conjugate head group are more effective in converting the neutral species of fluoroquinolones into a cationic species than NaDC. The quenching order is in accordance with hydrophobicity indices of bile salt.     

Natural convective heat transfer in water enclosed between pairs of differentially heated vertical plates

This paper presents the results of an experimental study of buoyancy-driven convective heat transfer between three parallel vertical plates, symmetrically spaced with water as the intervening medium. The centre plate was electrically heated, while the other side plates were water-cooled forming two successive parallel vertical channels of dimensions 20 cm × 3.5 cm × 35 cm (length W, gap L, height H) each. Top, bottom and sides of the channels were open to water in the chamber which is the novel aspect of this study. Plate surface temperature and bath temperature at different levels of height from the bottom of channel were measured by K-type thermocouples. Experimental data have been correlated as under:

Polymerization of Aniline by Auric Acid: Formation of Gold Decorated Polyaniline Nanoballs

Summary: We report a new method for the preparation of polyaniline nanoballs by using HAuCl₄ as an oxidizing agent. During the reaction, aniline is oxidized and forms polyaniline whilst the hydrogen tetrachloroaurate is reduced and forms gold nanoparticles. These gold nanoparticles are found to decorate the nanoballs.

The resultant precipitate and corresponding TEM image of the gold‐nanoparticle covered polyaniline nanoball.     

Correlation of Phosphorus Adsorption with Chemical Properties of Aluminum-Based Drinking Water Treatment Residuals Collected from Various Parts of the United States

Over the past several decades, the value of drinking water treatment residuals (WTRs), a byproduct of the coagulation process during water purification, has been recognized in various environmental applications, including sustainable remediation of phosphorus (P)-enriched soils. Aluminum-based WTRs (Al-WTRs) are suitable adsorbent materials for P, which can be obtained and processed inexpensively. However, given their heterogeneous nature, it is essential to identify an easily analyzable chemical property that can predict the capability of Al-WTRs to bind P before soil amendment. To address this issue, thirteen Al-WTRs were collected from various geographical locations around the United States. The non-hazardous nature of the Al-WTRs was ascertained first. Then, their P adsorption capacities were determined, and the chemical properties likely to influence their adsorption capacities were examined. Statistical models were built to identify a single property to best predict the P adsorption capacity of the Al-WTRs. Results show that all investigated Al-WTRs are safe for environmental applications, and oxalate-extractable aluminum is a significant indicator of the P adsorption capacity of Al-WTRs (p-value = 0.0002, R² = 0.7). This study is the first to report a simple chemical test that can be easily applied to predict the efficacy of Al-WTRs in binding P before their broadscale land application.     

Phosphorus and Heavy Metals Removal from Stormwater Runoff Using Granulated Industrial Waste for Retrofitting Catch Basins

Phosphorus and heavy metals are washed off and transported with stormwater runoff to nearby surface water bodies resulting in environmental and human health risks. Catch basins remain one of the primary gateways through which stormwater runoff and pollutants from urban areas are transported. Retrofitting catch basins to enhance their phosphorus and heavy metal removal can be an effective approach. In this study, aluminum-based water treatment residual (WTR, a non-hazardous byproduct of the water treatment process) was granulated via a green method to serve as a sustainable filter material, called WTR granules, for enhancing the capabilities of catch basins to remove phosphorus and heavy metals. The WTR granules were field tested in a parking lot in Hoboken, New Jersey. Twelve storm events were monitored. The results showed that the WTR granules significantly (p < 0.05) reduced dissolved P, Cu, and Zn, as well as total P, Cu, Pb, and Zn concentrations in stormwater runoff without signs of disintegration. No flooding or water ponding was observed during the implementation. Results suggest the WTR granules are an inexpensive, green filter material that can be used for retrofitting catch basins to remove phosphorus and heavy metals effectively.     

Short peptide-based cross-β amyloids exploit dual residues for phosphoesterase like activity

Herein, we report that short peptides are capable of exploiting their anti-parallel registry to access cross-β stacks to expose more than one catalytic residue, exhibiting the traits of advanced binding pockets of enzymes. Binding pockets decorated with more than one catalytic residue facilitate substrate binding and process kinetically unfavourable chemical transformations. The solvent-exposed guanidinium and imidazole moieties on the cross-β microphases synergistically bind to polarise and hydrolyse diverse kinetically stable model substrates of nucleases and phosphatase. Mutation of either histidine or arginine results in a drastic decline in the rate of hydrolysis. These results not only support the argument of short amyloid peptides as the earliest protein folds but also suggest their interactions with nucleic acid congeners, foreshadowing the mutualistic biopolymer relationships that fueled the chemical emergence of life.

Amyloid based short peptide assemblies use antiparallel registry to expose multiple catalytic residues to bind and cleave kinetically stable phosphoester bonds of nucleic acid congeners, foreshadowing interactions of protein folds with nucleic acids.     

Non-Equilibrium Polymerization of Cross-β Amyloid Peptides for Temporal Control of Electronic Properties

Hydrophobic collapse plays crucial roles in protein functions, from accessing the complex three-dimensional structures of native enzymes to the dynamic polymerization of non-equilibrium microtubules. However, hydrophobic collapse can also lead to the thermodynamically downhill aggregation of aberrant proteins, which has interestingly led to the development of a unique class of soft nanomaterials. There remain critical gaps in the understanding of the mechanisms of how hydrophobic collapse can regulate such aggregation. Demonstrated herein is a methodology for non-equilibrium amyloid polymerization through mutations of the core sequence of Aβ peptides by a thermodynamically activated moiety. An out of equilibrium state is realized because of the negative feedback from the transiently formed cross-β amyloid networks. Such non-equilibrium amyloid nanostructures were utilized to access temporal control over its electronic properties.