Dendrimer applications: a brief review

: Dendrimers are highly branched three-dimensional macromolecules with a highly controlled structure, a single molecular weight, numerous controllable dendritic branches and peripheral functionalities, as well as the tendency to adopt an ellipsoid or spheroid shape once a certain size is reached. These features have made them attractive for application in pharmaceutical and medicinal chemistry in gene transfection, as medical imaging agents, and as drug carriers in potential drug delivery agents. The incorporation of metallic species into dendritic molecules has also been reported; the focus has been on organometallic dendrimers with metallic species only at specific positions of the molecules, such as the core, dendritic branches and the periphery, studied for their magnetic, electronic, and photo-optical or catalytic properties. Dendrimers have been investigated for optoelectronic applications (adsorption, emission, laser emission, nonlinear optics) through the encapsulation of active units by dendritic branches, core and peripheral. This review briefly discusses their use in nanomedicine, cancer treatment, treatment of other diseases, tissue repair, catalysis and applications in OLEDs and solar cells.

Are Vapor-Like Fluids Viable Ore Fluids for Cu-Au-Mo Porphyry Ore Formation?

Ore formation in porphyry Cu-Au-(Mo) systems involves the exsolution of metal-bearing fluids from magmas and the transport of the metals in magmatic-hydrothermal plumes that are subject to pressure fluctuations. Deposition of ore minerals occurs as a result of cooling and decompression of the hydrothermal fluids in partly overlapping ore shells. In this study, we address the role of vapor-like fluids in porphyry ore formation through numerical simulations of metal transport using the Gibbs energy minimization software, GEM-Selektor. The thermodynamic properties of the hydrated gaseous metallic species necessary for modeling metal solubility in fluids of moderate density (100–300 kg/m3) were derived from the results of experiments that investigated the solubility of metals in aqueous HCl- and H2S-bearing vapors. Metal transport and precipitation were simulated numerically as a function of temperature, pressure, and fluid composition (S, Cl, and redox). The simulated metal concentrations and ratios are compared to those observed in vapor-like and intermediate-density fluid inclusions from porphyry ore deposits, as well as gas condensates from active volcanoes. The thermodynamically predicted solubility of Cu, Au, Ag, and Mo decreases during isothermal decompression. At elevated pressure, the simulated metal solubility is similar to the metal content measured in vapor-like and intermediate-density fluid inclusions from porphyry deposits (at ~200–1,800 bar). At ambient pressure, the metal solubility approaches the metal content measured in gas condensates from active volcanoes (at ~1 bar), which is several orders of magnitude lower than that in the high-pressure environment. During isochoric cooling, the simulated solubility of Cu, Ag, and Mo decreases, whereas that of Au reaches a maximum between 35 ppb and 2.6 ppm depending on fluid density and composition. Similar observations are made from a compilation of vapor-like and intermediate-density fluid inclusion data showing that Cu, Ag, and Mo contents decrease with decreasing P and T. Increasing the Cl concentration of the simulated fluid promotes the solubility of Cu, Ag, and Au chloride species. Molybdenum solubility is highest under oxidizing conditions and low S content, and gold solubility is elevated at intermediate redox conditions and elevated S content. The S content of the vapor-like fluid strongly affects metal ratios. Thus, there is a decrease in the Cu/Au ratio as the S content increases from 0.1 to 1 wt %, whereas the opposite is the case for the Mo/Ag ratio; at S contents of >1 wt %, the Mo/Ag ratio also decreases. In summary, thermodynamic calculations based on experiments involving gaseous metallic species predict that vapor-like fluids may transport and efficiently precipitate metals in concentrations sufficient to form porphyry ore deposits. Finally, the fluid composition and pressure-temperature evolution paths of vapor-like and intermediate-density fluids have a strong effect on metal solubility in porphyry systems and potentially exert an important control on their metal ratios and zoning.

Quantifying Crude Oil Contamination in Sand and Soil by EPR Spectroscopy

Crude oil frequently contains stable radicals that allow detection by means of EPR spectroscopy. On the other hand, most sands and soils possess significant amounts of iron, manganese or other metallic species that often provide excessively broad EPR signatures combined with well-defined sharp features by quartz defects. In this study, we demonstrate the feasibility to identify oil contamination in natural environments that are subject to oil spillage during production on land, as well as beachside accumulation of marine oil spillage. Straightforward identification of oil is enabled by the radical contributions of asphaltenes, in particular by vanadyl multiplets that are absent from natural soils. This potentially allows for high-throughput soil analysis or the application of mobile EPR scanners.

FactSage Modelling of Pb and Ni Speciation in Surface Water from Woji Creek, Rivers State, Nigeria

The present study is designed to use FactSage version 7.3 to simulate and predict the ionic speciation of lead (Pb) and nickel (Ni) in surface water sampled from Woji creek in Rivers State, Nigeria. Along the 3 km stretch (stations 1 to 5) of Woji creek, in-situ records were taken for temperature, pH and electrode potential (Eh); surface water samples to be assessed for Pb and Ni were collected in sterile bottles. Along the creek, surface water Eh is in the order: station 2 > station 4 > station 5 > station 3 = station 1, with mean value of Eh as 140 ± 20 mV. Surface water pH was close to neutral, and in line with: station 4 > station 2 > station 5 > station 1 > station 3; with 6.81 ± 0.13 as the mean value of pH. The trend of temperature values was recorded as: station 1 > station 2 = station 3 = station 4 > station 5; with the mean value deduced to be 25.6 ± 0.4. Mean concentration of Pb and Ni across the creek were 0.92 ± 0.27 mg/l and 0.46 ± 0.23 mg/l respectively. Pb species exists predominantly in the forms: Pb6(OH)84+(aq) (45%), Pb4(OH)44+(aq) (45%). Other forms of Pb present in the surface water are PbO(s) (5%), PbO2(s) (4%) and Pb2+(aq) (1%). NiO(s) had the highest proportion of Ni in the surface water (67%), followed by Ni(OH)2(s) (30%) and Ni2+(aq) (3%). The predicted metallic species could possibly be sorbet to particulates; thereby increase their chances of bioavailability and subsequent ingestion by fishes and other aquatic organisms. This will in turn influence their bioaccumulation via food chain and increase the tendency of risk impact on man and aquatic ecosystem.

Combined antioxidant capped and surface supported redox-sensitive nanoparticles for continuous elimination of multi-metallic species

A strategic modification involving (i) multi-functional almond shell biochar surface support and (ii) capping with almond skin extracted antioxidants was performed to preserve redox-sensitive Fe0 nanoparticles (NPs). pXRD data showed...

In situ creation of multi-metallic species inside porous silicate materials with tunable catalytic properties

Porous metal silicate (PMS) material PMS-11, consisting of uniformly distributed multi-metallic species inside the pores, is synthesized by using a discrete multi-metal coordination complex as the template, demonstrating high catalytic...

Ultrafast reproducible synthesis of an Agnanocluster@MOF composite and its superior visible-photocatalytic activity in batch and in continuous flow

The (photo)catalytical properties of Metal-Organic Frameworks (MOFs) can be enhanced by postsynthetic inclusion of metallic species in their porosity. Due to their extraordinarily high surface area and well defined porous...