Electrogenerated chemiluminescence of tris(2,2' bipyridine)ruthenium(ii) using common biological buffers as co-reactant, pH buffer and supporting electrolyte

A series of aliphatic tertiary amines (HEPES, POPSO, EPPS and BIS-TRIS) commonly used to buffer the pH in biological experiments, were examined as alternative, non-toxic co-reactants for the electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(ii) ([Ru(bpy)3](2+)). These were found to be very attractive as "multi-tasking" reagents, serving not only as co-reactants, but also fulfiling the roles of pH buffer and supporting electrolyte within an aqueous environment; thus significantly simplifying the overall ECL analysis. Sub-nanomolar detection limits were obtained for [Ru(bpy)3](2+) in the presence of BIS-TRIS, making this species an valuable option for co-reactant ECL-based bioanalytical applications.

Investigating the effect of solution pH on speciation of La(4OH-cin)3 with correlation to electrochemical behaviour and corrosion efficiency

The nature of the species in solution plays a major role on the effectiveness of the corrosion inhibitor on a steel substrate. The speciation of lanthanum 4-hydroxy cinnamate (La(4OHCin) ₃) in solution has been evaluated using experimental techniques composed of potentiodynamic polarisation, immersion tests, nuclear magnetic spectroscopy and mass spectroscopy. It is evident that the species in solution are dependent on pH and this impacts the corrosion inhibition mechanism and the efficiency. It was found that at a neutral pH of 5.5 the La(4OH-Cin)₃ behaves as a strong anodic inhibitor. Whereas, when the pH shifts to low (pH2.5) and/or high (pH8) the corrosion mechanism changes.

Removal of arsenic from contaminated soils using different salt extractants

This study presents an environmental-friendly and cost effective method for the extraction of arsenic from contaminated soils.
Laboratory experiments using inorganic salts, potassium phosphate (KH2PO4), potassium chloride (KCl), potassium nitrate (KNO3), potassium sulfate (K2SO4), and sodium perchlorate (NaClO4) were evaluated as arsenic extractants. An Andosol soil was artificially contaminated with arsenite [As(III)] and arsenate [As(V)]. The soil was washed in a batch process with different salt solutions in the pH range 3–11 for 24 hours at 20◦C. Among the various potassium and sodium salts tested, KH2PO4 was found to be highly effective in extracting arsenic from As(III)-soil attaining more than 80% and 40% from As(V)-soil in neutral pH range. Other salts were particularly ineffective in extraction of arsenic from both soils. More arsenic was extracted more from the As(III)-soil than the As(V)-soil.

The nature of the surface film on steel treated with cerium and lanthanum cinnamate based corrosion inhibitors

The corrosion inhibition mechanisms of new cerium and lanthanum cinnamate based compounds have been investigated through the surface characterisation of the steel exposed to NaCl solution of neutral pH. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to identify the nature of the deposits on the metal surface and demonstrated that after accelerated tests the corrosion product commonly observed on steel (i.e. lepidocrocite, γ-FeOOH) is absent. The cinnamate species were clearly present on the steel surface upon exposure to NaCl solution for short periods and appeared to coordinate through the iron. At longer times the Rare Earth Metal (REM) oxyhydroxide species are proposed to form as identified through the bands in the 1400–1500 cm⁻¹ region. These latter bands have been previously assigned to carbonate species adsorbed onto REM oxyhydroxide surfaces. The protection mechanism appears to involve the adsorption of the REM–cinnamate complex followed by the hydrolysis of the REM to form a barrier oxide on the steel surface.

The impact of textile wet colouration on the environment in 2011

Wet textile colouration has the highest environmental impact of all textile processing steps. It consumes water, chemicals and energy and produces liquid, heat and gas waste streams. Liquid effluent streams are often quite toxic to the environment. There are a number of different dyeing processes, normally fibre type specific, and each has a different impact on the environment. This research investigated the energy, chemical and water requirements for the exhaust colouration of cotton, wool, polyester and nylon. The research investigated the liquid waste biological and chemical oxygen demand, salinity, pH and colour along with the energy required for drying after colouration. Polyester fibres had the lowest impact on the environment with lowest water and energy consumption in dyeing, good dye bath exhaustion, the lowest salinity levels in their effluent, relatively neutral pH effluent and low energy in drying. The wool and nylon had similar dye bath requirements and outputs however the nylon could be dyed at far lower liquor ratios and hence provided better energy and water use figures. The cotton and wool required high energy consumption in drying after colouration. Cotton performed poorly in all of the measured parameters.

The impact of textile wet colouration on the environment in 2011

Wet textile colouration has the highest environmental impact of all textile processing steps. It consumes water, chemicals and energy and produces liquid, heat and gas waste streams. Liquid effluent streams are often quite toxic to the environment. There are a number of different dyeing processes, normally fibre type specific, and each has a different impact on the environment. This research investigated the energy, chemical and water requirements for the exhaust colouration of cotton, wool, polyester and nylon. The research investigated the liquid waste biological oxygen demand, total organic carbon dissolved solids, suspended solids, pH and colour along with the energy required for drying after colouration. Polyester fibres had the lowest impact on the environment with low water and energy consumption in dyeing, good dye bath exhaustion, the lowest dissolved solids levels in waste water, relatively neutral pH effluent and low energy in drying. The wool and nylon had similar dyebath requirements and outputs however the nylon could be dyed at far lower liquor ratios and hence provided better energy and water use figures. Cotton performed badly in all of the measured parameters.

Binding affinities of amino acid analogues at the charged aqueous titania interface : implications for titania-binding peptides

Despite the extensive utilization of biomolecule-titania interfaces, biomolecular recognition and interactions at the aqueous titania interface remain far from being fully understood. Here, atomistic molecular dynamics simulations, in partnership with metadynamics, are used to calculate the free energy of adsorption of different amino acid side chain analogues at the negatively-charged aqueous rutile TiO2 (110) interface, under conditions corresponding with neutral pH. Our calculations predict that charged amino acid analogues have a relatively high affinity to the titania surface, with the arginine analogue predicted to be the strongest binder. Interactions between uncharged amino acid analogues and titania are found to be repulsive or weak at best. All of the residues that bound to the negatively-charged interface show a relatively stronger adsorption compared with the charge-neutral interface, including the negatively-charged analogue. Of the analogues that are found to bind to the titania surface, the rank ordering of the binding affinities is predicted to be "arginine" > "lysine" ≈ aspartic acid > "serine". This is the same ordering as was found previously for the charge-neutral aqueous titania interface. Our results show very good agreement with available experimental data and can provide a baseline for the interpretation of peptide-TiO2 adsorption data.

A review of techniques for the monitoring of cathodic shielding and corrosion under disbonded coatings

The mitigation of external corrosion of energy pipelines by a combination of barrier coatings and Cathodic Protection (CP) is not always effective. Even when design specifications are properly met, the shielding of cathodic protection current from reaching steel surface by disbonded barrier coatings, often referred to as cathodic shielding, may lead to severe corrosion problems such as deep pitting, high and near neutral pH Stress Corrosion Cracking (SCC) and Microbiologically Induced Corrosion (MIC). Unfortunately, current indirect assessment methods used in the pipeline industry have serious difficulties in detecting such corrosion problems. This paper provides a brief review of current techniques and their limitations when being applied under complex buried pipeline environmental conditions. The main purpose is to identify potential methods that could be utilised in the design of new monitoring probes specific for the monitoring of cathodic shielding and corrosion of disbonded coatings in the pipeline industry.

Structure and properties of citrate overlayers adsorbed at the aqueous Au(111) interface.

One of the most common means of gold nanoparticle (AuNP) biofunctionalization involves the manipulation of precursor citrate-capped AuNPs via ligand displacement. However, the molecular-level structural characteristics of the citrate overlayer adsorbed at the aqueous Au interface at neutral pH remain largely unknown. Access to atomistic-scale details of these interfaces will contribute much needed insight into how AuNPs can be manipulated and exploited in aqueous solution. Here, the structures of such citrate overlayers adsorbed at the aqueous Au(111) interface at pH 7 are predicted and characterized using atomistic molecular dynamics simulations, for a range of citrate surface densities. We find that the overlayers are disordered in the surface density range considered, and that many of their key characteristics are invariant with surface density. In particular, we predict the overlayers to have 3-D, rather than 2-D, morphologies, with the anions closest to the gold surface being oriented with their carboxylate groups pointing away from the surface. We predict both striped and island morphologies for our overlayers, depending on the citrate surface density, and in all cases we find bare patches of the gold surface are present. Our simulations suggest that both citrate-gold adsorption and citrate-counterion pairing contribute to the stability of these citrate overlayer morphologies. We also calculate the free energy of adsorption at the aqueous Au(111) interface of a single citrate molecule, and compare this with the corresponding value for a single arginine molecule. These findings enable us to predict the conditions under which ligand displacement of surface-adsorbed citrate by arginine may take place. Our findings represent the first steps toward elucidating a more elaborate, detailed atomistic-scale model relating to the biofunctionalization of citrate-capped AuNPs.

Diorganotin dications stabilized by neutral ligands in the solid state: [R2Sn(H2O)2(OPPh3)2](O3SCF3)2 (R = Me, Bu)

The synthesis of [R₂Sn(H₂O)₂(OPPh₃)₂](O₃SCF₃)₂ (R = Me (1), Bu (2)) by the consecutive reaction of R₂SnO (R = Me, Bu) with triflic acid and Ph₃PO is described. Compounds 1 and 2 feature dialkyltin(IV) dications [R₂Sn(H₂O)₂(OPPh₃)₂]^₂+ apparently stabilized by the neutral ligands in the solid state. Compounds 1 and 2 readily dehydrate upon heating at 105 and 86 °C, respectively. The preparative dehydration of 1 afforded [Me₂Sn(OPPh₃)₂(O₃SCF₃)](O₃SCF₃) (1a), which features both bidentate and non-coordinating triflate anions. In compounds 1 and 2 the ligands Ph₃PO and H₂O are kinetically labile in solution and undergo reversible ligand exchange reactions. Compounds 1, 1a and 2 were characterized by multinuclear solution and solid-state NMR spectroscopy, IR spectroscopy, electrospray mass spectrometry, conductivity measurements, thermogravimetry and X-ray crystallography.

Monolayer behavior of a pyridyl head-group-containing amphiphile and its miscibility with poly(D,L-lactide-co-glycolide) on different pH subphase

In this paper, we investigated the Langmuir film and Langmuir–Blodgett (LB) monolayer film of a nonionic amphiphilic molecule, 4-(6-p-pyridyloxyl)hexyloxyl-4′-dodecyloxylazobenzene (C12AzoC6Py) and its mixture with poly(d,l-lactide-co-glycolide) (PLG) at different subphase pH values (2.0, 2.6, 3.3, 4.4, and 6.5, respectively) by surface pressure–area (π–A) isotherms, in situ interface Brewster angle microscopy (BAM), and ex situ atomic force microscopy (AFM). For pure C12AzoC6Py, its π–A isotherms display a plateau when the subphase pH value is lower than 3.0. The pressure of the plateau increases with the decrease of pH until 2.0. Over the plateau, the π–A isotherms become almost identical to the one under neutral conditions. The appearance of such a plateau can be explained as the coexistence of protonation and unprotonation of pyridyl head groups of the employed amphiphile. In contrast to the homogeneous surface morphology of pure C12AzoC6Py near the plateau by BAM observation, the surface in the case of its mixing with PLG exhibits a dendritic crystalline state under low surface pressure at subphase pH lower than 3.0. The crystalline state becomes soft and gradually melts into homogeneous aggregates with surface pressure increasing to a higher value than that of the plateau. Meanwhile, the hydrolysis of PLG in the mixture system at the interface has been affirmed to be restrained to a very large extent. And the PLG was believed to be compelled to the up layer of the LB film due to the phase separation, which is examined by AFM. Based on the experimental results, the corresponding discussion was also performed.

Fluorine-free superhydrophobic coatings with pH-induced wettability transition for controllable oil-water separation

We present a simple, environmentally friendly approach to fabricating superhydrophobic coatings with pH-induced wettability transition. The coatings are prepared from a mixture of silica nanoparticles and decanoic acid-modified TiO2. When the coating is applied on cotton fabric, the fabric turns superhydrophobic in air but superoleophilic in neutral aqueous environment. It is permeable to oil fluids but impermeable to water. However, when the coated fabric is placed in basic aqueous solution or ammonia vapor, it turns hydrophilic but underwater superoleophobic, thus allowing water to penetrate through but blocking oil. Therefore, such a unique, selective water/oil permeation feature makes the treated fabric have capability to separate either oil or water from a water-oil mixture. It may be useful for development of smart oil-water separators, microfluidic valves, and lab-on-a-chip devices.