Inclusion chemistry of neutral nonlinear optical dyes within organically modified silicates

The field of photonics involves the use of light to acquire, store, process, and transmit information. Nonlinear optical (NLO) materials are crucial for success in the advancement of photonic devices. Laponite and hectorite host assemblies have been shown previously by our group to induce I -aggregation of nonlinear optical (NLO) dyes and offer facile routes to film fabrication. Head-to-tail alignment (J-aggregation) of the NLO chromophores is a required condition for photonic applications. In this study, tetrabutylammonium, triethylhexylammonium, trimethyldodecylammonium, and trimetylcetylarunonium surfactants were utilized to render the smectic intergallery region organophilic thus facilitating chromophore intercalation and an increased J-aggregated dye fraction. Fourier transform infrared spectroscopy and powder X-ray diffraction were used to probe the interlayer structure and phase state of the intercalated alkylammonium surfactants by monitoring frequency shifts of the CH2 stretching vibrations and gallery height as a function of packing density and chain length. As the chain length or interlayer packing density increased, the chains adopted a more ordered, lamellar structure leading to two-dimensional ordering of clay tactoids. Organically modified laponite was subsequently loaded with two NLO chromophores, disperse red! (DSRI) and disperse orange 3 (DS03), and the effects of surfactants on the extent of J-aggregation were studied. The nature of dye aggregation was characterized using UVNIS spectroscopy. We report herein that modifying laponite tactoids with surfactants allows for selective control over nonlinear optical chromophore aggregation. In addition, the presence of surfactant within the host framework affords the possibility of higher dye loadings ofDS03 and DSRI as well as inducing a higher fraction of J-aggregates of DSRI than previously reported

EFFECTS OF LOW-DOSAGE LIME TREATMENT ON BENEFICIAL REUSE OF POND ASH AS SECONDARY CEMENTITIOUS MATERIALS (SCMS)

Effects of low-dosage lime treatment on beneficial reuse of pond ash as Secondary Cementitious Materials (SCMs) Authors Mr. Howard Fitzgerald - United States - Lhoist Mr. Utsa Rashique - United States - Lhoist Mrs. Karen Slade - United States - Lhoist Mr. Ian Saratovsky - United States - Lhoist Abstract Lime treatment is an effective way to dehydrate and solidify ponded coal ash, facilitating easier handling and transportation to, and compaction in a landfill. However, questions arise regarding the impact of low lime dosage on the future beneficial reuse of the treated pond ash. One such potential beneficial reuse case is its application as a Secondary Cementitious Material (SCM), especially as a pozzolan grade fly ash for mortars and for ready mixed concrete production. Given the retirement of coal fired power plants and the resulting reduction in fresh, as-produced fly ash, exploring alternatives like reclamation and beneficial reuse of ponded ash is crucial. This study investigates the feasibility of lime-treated pond ash as a pozzolan grade fly ash. The physical and chemical properties of the treated pond ash are compared to ASTM C618 standards, showing a good match. The study involved replacing various percentages of Portland Cement in a type S masonry mortar mix with the treated pond ash sample. Testing revealed satisfactory short- and long-term strength performance, along with excellent results in various other parameters like water retention, water demand, setting time, and other properties. Overall, lime-treated pond ash proved to be a potentially effective SCM in a standard mortar mix. This is a strong indicator that low dosage lime treatment of ponded ash will not adversely impact its beneficial use as an SCM in the future

Manganese-oxidizing bacteria mediate the degradation of 17α-ethinylestradiol

Manganese (II) and manganese-oxidizing bacteria were used as an efficient biological system for the degradation of the xenoestrogen 17 alpha-ethinylestradiol (EE2) at trace concentrations. Mn(2+)-derived higher oxidation states of Mn (Mn(3+), Mn(4+)) by Mn(2+)-oxidizing bacteria mediate the oxidative cleavage of the polycyclic target compound EE2. The presence of manganese (II) was found to be essential for the degradation of EE2 by Leptothrix discophora, Pseudomonas putida MB1, P. putida MB6 and P. putida MB29. Mn(2+)-dependent degradation of EE2 was found to be a slow process, which requires multi-fold excess of Mn(2+) and occurs in the late stationary phase of growth, implying a chemical process taking place. EE2-derived degradation products were shown to no longer exhibit undesirable estrogenic activity

Nucleation and growth of todorokite from birnessite: Implications for trace-metal cycling in marine sediments

The phyllomanganate birnessite is the main Mn-bearing phase in oxic marine sediments, and through coupled sorption and redox exerts a strong control on the oceanic concentration of micronutrient trace metals. However, under diagenesis and mild hydrothermal conditions, birnessite undergoes transformation to the tectomanganate todorokite. The mechanistic details of this transformation are important for the speciation and mobility of metals sequestered by birnessite, and are necessary in order to quantify the role of marine sediments in global trace element cycles. Here we transform a synthetic, poorly crystalline, hexagonal birnessite, analogous to marine birnessite, into todorokite under a mild reflux procedure, developed to mimic marine diagenesis and mild hydrothermal conditions. We characterize our birnessite and reflux products as a time series, employing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET surface area analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and extended X-ray absorption fine structure spectroscopy (EXAFS). We provide new insight into the crystallization pathway and mechanism of todorokite formation from birnessite under conditions analogous to those found in marine diagenetic and hydrothermal settings. Specifically we propose a new four-stage process for the transformation of birnessite to todorokite, beginning with todorokite nucleation, then crystal growth from solution to form todorokite primary particles, followed by their self-assembly and oriented growth via oriented attachment to form crystalline todorokite laths, culminating in traditional crystal ripening. We suggest that, contrary to current understanding, trace metals like Ni might retard the transformation of birnessite to todorokite and be released to marine sedimentary pore-waters during this diagenetic process, thus potentially providing a benthic flux of these micronutrients to seawater