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Fluorescence-guided surgery (FGS) is an emerging technique for tissue visualization during surgical procedures. Structures of interest are labeled with exogenous probes whose fluorescent emissions are acquired and viewed in real-time with optical imaging systems. This study investigated rare-earth-doped albumin-encapsulated nanocomposites (REANCs) as short-wave infrared emitting contrast agents for FGS. Experiments were conducted using an animal model of 4T1 breast cancer. The signal-to-background ratio (SBR) obtained with REANCs was compared to values obtained using indocyanine green (ICG), a near-infrared dye used in clinical practice. Prior to resection, the SBR for tumors following intratumoral administration of REANCs was significantly higher than for tumors injected with ICG. Following FGS, evaluation of fluorescence intensity levels in excised tumors and at the surgical bed demonstrated higher contrast between tissues at these sites with REANC contrast than ICG. REANCs also demonstrated excellent photostability over 2 hours of continuous illumination, as well as the ability to perform FGS under ambient lighting, establishing these nanocomposites as a promising contrast agent for FGS applications.

Epitaxial thin and thick lead zirconate titanate (PZT) films with the composition of PbZr0.7Ti0.3O3 were grown onto single-crystal SrTiO3 (100), (111), and (110) substrates using both microwave and conventional hydrothermal methods at 90–180°C from amorphous Zr-Ti hydrous oxide and lead acetate precursors. Different bases, such as KOH, NaOH, and tetramethylammonium hydroxide pentahydrate (TMAH) were used to study the effect of mineralizer type on the film quality and morphology. The impact of substrate surface modification on PZT nucleation and film growth was examined through chemical etching or pre-coating the substrate with a RF-sputtered thin PZT layer. Thick PZT film (~27 µm in thickness) was successfully synthesized by periodic replenishment of the reaction nutrient. Moreover, according to the collected kinetic data for microwave hydrothermal reactions, a microwave continuous-flow reactor operating at ≈ 300°C may be used to grow PZT films with the thickness of the order of 1 mm.

Current methods of rare earth element (REE) recovery from industrial solutions are environmentally untenable and have significant waste management challenges. Increasing global REE consumption necessitates the development of new, sustainable means of production. Herein, we report a means of recovering aqueous REEs using monoethanolamine and carbon dioxide as predicted using the Mixed-Solvent Electrolyte thermodynamic model. Validation experiments have demonstrated the > 99% recovery of Nd3+ as its normal carbonate, with the filtrate containing monoethanolamine hydrogen chloride. Additional experimentation also demonstrated the > 99% recovery of aqueous La3+ and Y3+ as their respective normal carbonates. These findings demonstrate that a thermodynamic simulation engine may be used to decrease the number of empirically driven experiments required to develop a new, high yield REE recovery unit operation that is applicable to concentrated and dilute aqueous solutions typical of industrial streams.

Leaching of six individual rare earth (yttrium, cerium, neodymium, samarium, europium, and ytterbium) doped synthetic phosphogypsum samples using a suite of lixiviants was conducted. The lixiviants chosen for this study were phosphoric acid, sulfuric acid, gluconic acid, and a “biolixiviant” consisting of spent medium containing organic acids from the growth of the bacterium Gluconobacter oxydans on glucose. The biolixiviant had a pH of 2.1 and the dominant organic acid was determined to be gluconic acid, present at a concentration of 220 mM. The leaching behaviors of the studied lixiviants were compared and rationalized by thermodynamic simulations. The results suggest that at equivalent molar concentrations of 220 mM the biolixiviant was more efficient at rare earth element (REE) extraction than gluconic acid and phosphoric acid but less efficient than sulfuric acid. Unlike the organic acids, at pH 2.1 the mineral acids failed to extract REE, likely due to different complexation and kinetic effects.

A thermodynamic model has been developed for calculating the phase behavior and caloric properties of rare earth elements in multicomponent sulfate solutions over wide ranges of temperature (up to 300 °C) at concentrations extending to solid–liquid saturation. The model has been constructed using the previously developed Mixed-Solvent Electrolyte (MSE) framework, which combines the standard-state thermochemical properties of aqueous and solid species with an ion-interaction formulation for the excess Gibbs energy. The model accurately reproduces the properties of binary aqueous rare earth sulfate solutions and multicomponent systems that include sulfuric acid and/or sodium sulfate. Solid-liquid phase diagrams have been constructed to elucidate the solubility of both stable and metastable solid phases. Regularities in the solubility behavior have been identified as a function of the cation radius for rare earth sulfates and double sodium-rare earth sulfate salts. The solubility of rare earth sulfates at ambient conditions shows an s-shape pattern with a local maximum at Pr, followed by a plateau between Sm and Tb and then an increase starting from Tb. On the other hand, the double salts REE2Na2(SO4)4 show a solubility minimum at Pr, followed by a strong increase in solubility for heavier rare earths. For the double sulfate salts for which no experimental data are available, solubilities have been estimated using an analysis of trends in thermochemical properties across the lanthanide series. The model is part of a systematic effort to develop a comprehensive treatment of the properties of rare earth salt solutions to facilitate the design and optimization of processes for the recovery of rare earth elements.

Recycling electronic scrap is a significant source of rare earth metals. Whereas traditional recycling routes for some electronic scrap emphasize the recovery of silver and gold, value can be attained by recovering of rare earth elements from unique feed streams. This paper describes a hydrometallurgical process for the recovery of rare earth elements from hard disk drives using HCl as a re-usable extraction medium. The mixture was selectively leached using HCl to remove the magnet alloy coating from shredded hard disk drives. The dissolved rare earth elements were precipitated using sodium sulfate, recovered as the sodium double salt, and subsequentially converted to hydroxides. The recovery of rare earth elements is consistent with amounts predicted using a thermodynamic model based on the MSE (Mixed-Solvent Electrolyte) framework of precipitated double salts. The effect of HCl concentration was measured upon the magnet dissolution rate. In addition, the leaching rates for steel were evaluated and found to be three orders of magnitude lower than the magnet alloy. An automated system was used to control leachate pH. The magnet and steel dissolution rate were examined for various HCl concentrations. The recovery of rare earth hydroxides was over 80%.

Sodium rare earth fluorides, NaREF4 (RE = rare earth), are used as luminescent materials for light emission and biomedical applications and are important compositions for extracting and separating RE elements. Solution calorimetric measurements of a series of β-structured NaREF4 (Na1.5RE1.5F6) phases with various RE elements determined their heats of formation. Though the lattice contracts from light to heavy RE elements, NaREF4 compounds show more exothermic enthalpies of formation from binary components with decrease of RE3+ radius, contrary to behavior seen in most RE oxide ternary compounds. By constructing Born–Haber cycles, the different slopes of lines relating lattice energies to lattice parameters in binary and ternary fluorides appear to be the reason for this reverse trend, which can be associated with changes in the coordination number of RE cations. These trends and the metastability of sodium light RE fluorides not only reveal the key role of ionic radius in RE compound stability, but also are significant for the design and synthesis of new materials and motivate the more effective utilization of RE.

(DME)2Ln(SeC6F5)3 (Ln = Nd, Er, Tm) can be isolated in high yield by reductive cleavage of the Se-Se bond in (SeC6F5)2 with elemental Ln in DME. All three Ln compounds are isostructural, with 8 coordinate Ln bound to four O from DME, three terminally bound Se(C6F5), and a dative bond from an arene fluoride to a fluorine at the ortho position of one selenolate. Emission measurements indicate that these compounds are bright NIR sources.

Rare earth elements (REE) are technology drivers, essential for applications ranging from clean energy technologies to biomedical imaging. Thus they are “critical elements” and it is desirable to find additional RE domestic sources and explore green extraction technologies to overcome their supply risk. Phosphogypsum, a major byproduct of the phosphate fertilizer industry, incorporates a significant amount of RE from the apatite source rock and thus is a potential alternate source of RE. To know the accessibility and extractability of RE from phosphogypsum, it is important to understand the location and nature of RE binding. Here, we report the synthesis of analogs of RE-doped phosphogypsum, with europium (Eu) as a model RE. Using several characterization tools we conclude that the majority of Eu is on the surface of the calcium sulfate crystal as a separate secondary phase, namely a metastable amorphous/nanocrystalline precipitate in which Eu is associated with phosphate and sulfate as counterbalancing ions. The rapid precipitation at low temperature could be responsible for this behavior, which may not represent equilibrium, and our experiments are comparable in the timescale with the fast phosphogypsum precipitation in the industrial process. These results suggest that the Eu is not entrapped by ionic substitutions in the calcium sulfate lattice. Thus RE should be extracted relatively easily from phosphogypsum using methods that extract the RE from its surface.

Bastnaesite, [RE-CO 3 -OH/F] (RE = rare earth) is one of the major sources of rare earth elements found in commercial deposits at Mountain Pass, California, Bayan Obo, China, and elsewhere. Synthetic forms of bastnaesite have been explored for applications including optical devices and phosphors. Determination of thermodynamic properties of these phases is critical for understanding their origin, mining, and processing. We report the first experimental determination of formation enthalpies of several OH and F bastnaesites based on high-temperature oxide melt solution calorimetry of well-characterized synthetic samples. The formation enthalpies from binary oxides and fluorides for all the bastnaesite samples are highly exothermic, consistent with their stability in the garnet zone of the Earth’s crust. Fluoride bastnaesite, which is more abundant in nature than its hydroxide counterpart, is thermodynamically more stable. For both OH and F bastnaesite, the enthalpy of formation becomes more negative with increasing ionic radius of the RE 3+ cation. This periodic trend is also observed among rare earth phosphates and several other rare earth ternary oxides. For a given RE, the formation enthalpies from binary oxides are more negative for orthophosphates than for bastnaesites, supporting the argument that monazite could have formed by reaction of bastnaesite and apatite at high temperature. The difference in formation enthalpy of monazite and bastnaesite provides insight into energetics of such reactions along the rare earth series.

High-refractive-index ZrO2 nanoparticles were used to tailor the refractive index of a polymer matrix to match that of luminescent lanthanide-ion-doped (La0.92Yb0.075Er0.005F3) light-emitting particles, thereby reducing scattering losses to yield highly transparent emissive composites. Photopolymerization of blends of an amine-modified poly(ether acrylate) oligomer and tailored quantities of ZrO2 nanoparticles yielded optically transparent composites with tailored refractive indices between 1.49 and 1.69. By matching the refractive index of the matrix to that of La0.92Yb0.075Er0.005F3, composites with high transmittance (>85%) and low haze from the visible to infrared regions, bright 1530 nm optical emissions were achieved at solids loadings of La0.92Yb0.075Er0.005F3, ranging from 5 to 30 vol %. These optical results suggest that a hybrid matrix approach is a versatile strategy for the fabrication of functional luminescent optical composites of high transparency.

Seasonal and spatial variations of the light absorption coefficient, a(λ), were investigated in the New York/New Jersey Harbor Estuary (i.e., Jamaica Bay, Hudson/Raritan Bay, and Inner Harbor) from August 2008 through June 2009 to characterize the bio-optical characteristics of the estuary. The nonalgal particles (NAP) made a constant light absorption contribution of 18 ± 6% (mean ± standard deviation) (440 nm) over the entire estuary. Covariation among chlorophyll a, total suspended solid, and colored dissolved organic matter (CDOM) was not observed, indicating optical complexity of the estuary. Two optical domains were observed: a phytoplankton-dominated regime (Jamaica Bay) and a CDOM dominated regime (Inner Harbor and Hudson/Raritan Bay). Specific absorption coefficient a ph * (λ) decreased with increasing chlorophyll a; this was due to the large cell sizes of diatoms based on package effect analysis. The sources of CDOM and NAP were terrestrial and of in situ origins, respectively. The slopes of CDOM (S CDOM) and NAP (S NAP) of the estuary were reported for the first time. Overall, this study provided the most complete characterization of light absorption for the New York/New Jersey Harbor Estuary, which will provide critical parameters and insights to build/refine remote sensing models for monitoring water quality in the estuary.

Hydrothermal and commercial barium titanate powders were examined for undesirable impurity phases. Compositional differences in the powder were evaluated using x-ray diffraction (XRD), x-ray fluorescence (XRF), and x-ray photoelectron spectroscopy (XPS). A barium-rich impurity phase, virtually undetectable by XRD, was detected via XPS. Barium impurity phase peaks were detected at binding energies @1.5 eV higher than those characteristic of barium in a barium titanate bonding state for both the Ba 3d and Ba 4d transitions. Simple curve-fitting techniques were used to quantify the percentage of barium in a barium titanate bonding state versus another barium bonding state for each set of doublets. The barium impurity bonding state accounted for 20-50 mol% of the barium detected by XPS.

Riman, Richard Eric/0000-0002-4289-5768; Vakifahmetoglu, Cekdar/0000-0003-1222-4362 WOS:000326712200047 Acmite (NaFeSi2O6) films were formed on steel coupons via solvothermal reaction of silica, sodium hydroxide, and 1, 4-butanediol in an autoclave under autogenous pressure. Systematic variation in processing variables led to homogenous coatings comprised of pinacoidal acmite grains with an average grain size of similar to 33m. The coatings were produced on the steel coupons from reactant conditions of 0.635m SiO2, 2.546m NaOH, and 3.087m 1,4-butanediol for 72h at 240 degrees C. DOW Chemical Corporation; PPG Corporation The authors acknowledge Dr. Hebert of Materials Science and Engineering at University of Connecticut for his aid in analyzing the metal-ceramic interface with FIB and EDS techniques. Support for this work was received from DOW Chemical Corporation and PPG Corporation.

With the increasing demand for rare earth elements (REEs) in many emerging clean energy technologies, there is an urgent need for the development of new approaches for efficient REE extraction and recovery. As a step toward this goal, we genetically engineered the aerobic bacterium Caulobacter crescentus for REE adsorption through high-density cell surface display of lanthanide binding tags (LBTs) on its S-layer. The LBT-displayed strains exhibited enhanced adsorption of REEs compared to cells lacking LBT, high specificity for REEs, and an adsorption preference for REEs with small atomic radii. Adsorbed Tb(3+) could be effectively recovered using citrate, consistent with thermodynamic speciation calculations that predicted strong complexation of Tb(3+) by citrate. No reduction in Tb(3+) adsorption capacity was observed following citrate elution, enabling consecutive adsorption/desorption cycles. The LBT-displayed strain was effective for extracting REEs from the acid leachate of core samples collected at a prospective rare earth mine. Our collective results demonstrate a rapid, efficient, and reversible process for REE adsorption with potential industrial application for REE enrichment and separation.

Infrared-to-visible rare earth doped upconversion phosphors that convert multiple photons of lower energy to higher energy photons offer a wide range of technological applications. The brightness (i.e., emission intensities) and energy efficiency of phosphors are important performance characteristics that determine which applications are appropriate. Optical efficiency can be used as a measure of the upconversion emission performance of these rare earth doped phosphors. In this work, hexagonal-phase NaYF(4):Yb-Er was synthesized using the hydrothermal method in the presence of surfactants like trioctylphosphine, polyethylene glycol monooleate, and polyvinylpyrrolidone. The upconversion emission optical efficiencies of NaYF(4):Yb-Er were measured to quantify and evaluate the effects of surface coatings and accurately reflect the brightness and energy efficiency of these phosphors. Polyvinylpyrrolidone-modified NaYF(4):Yb-Er particles were found to be ~5 times more efficient and brighter than the unmodified particles. The difference in efficiency was attributed to reduced reflectance losses at the particle-air interface via refractive index mismatch reduction between the core NaYF(4):Yb-Er particles and air using polyvinylpyrrolidone as a surfactant.

Dicalcium phosphate anhydrous (DCPA) and dicalcium phosphate dihydrate (DCPD) particles were prepared through the reaction between calcium nitrate and dipotassium hydrogen phosphate in a solution and a multiple emulsion. Organic compounds were added into the phosphate solution with the aim of modifying the morphology. Large parallelogrammic particles of DCPD were obtained with no additive. By adding 2- aminoethanol, the product was changed to rhombic in shape and reduced to one-twentieth in size, and the phase was DCPA. In the multiple emulsion, microspheres composed of DCPA were prepared. They were constructed by flaky, primary particles. The crystalline phase and morphology were affected by the concentrations of surfactants in the oil and outer aqueous phases.

Ln(SePh)(3) (Ln = Ce, Pr, Nd) reacts with elemental Se in the presence of Na ions to give (py)(16)Ln(17)NaSe(18)(SePh)(16), a spherical cluster with a 1 nm diameter. All three rare-earth metals form isostructural products. The molecular structure contains a central Ln ion surrounded by eight five-coordinate Se(2-) that are then surrounded by a group of 16 Ln that define the cluster surface, with additional μ(3) and μ(5) Se(2-), μ(3) and μ(4) SePh(-), and pyridine donors saturating the vacant coordination sites of the surface Ln, and a Na ion coordinating to selenolates, a selenido, and pyridine ligands. NIR emission studies of the Nd compound reveal that this material has a 35% quantum efficiency, with four transitions from the excited state (4)F(3/2) ion to (4)I(9/2), (4)I(11/2), (4)I(13/2), and (4)I(15/2) states clearly evident. The presence of Na(+) is key to the formation of these larger clusters, where reactions using identical concentrations of Nd(SePh)(3) and Se with either Li or K led only to the isolation of (py)(8)Nd(8)Se(6)(SePh)(12).

The aim of this study was to evaluate the bioactivity of hydroxyapatite films composed of hexagonal single crystals that display $$ \left\{ {10\bar{1}0} \right\} $$ and {0001} crystallographic faces. The effect of engineered [0001] crystallographic orientation was investigated in parallel. Films were deposited by triethyl phosphate/ethylenediamine-tetraacetic acid doubly regulated hydrothermal crystallization on Ti6Al4V substrates (10, 14, 24 h). Bioactivity was investigated by analysis of MC3T3-E1 pre-osteoblast spreading using scanning electron microscopy and quantitative analysis of cell metabolic activity (Alamar BlueTM) (0–28 days). Scanning electron microscopy and X-ray diffraction were used to evaluate the ability of films to support the differentiation of MC3T3-E1 pre-osteoblasts into matrix-secreting, mineralizing osteoblasts. Results demonstrated that all films enabled MC3T3-E1 cells to spread, grow, and differentiate into matrix-secreting osteoblasts, which deposited biomineral that could not be removed after extraction of organic material. Differences in [0001] HA crystallographic orientation were not, however, found to significantly affect bioactivity. Based on these results, it is concluded that these hydrothermal hydroxyapatite films are non-toxic, bioactive, osteoconductive, and biomineral bonding. The lack of a relationship between reported hydroxyapatite crystallographic face specific protein adsorption and bulk HA bioactivity are discussed in terms of crystallographic texture, surface roughness, assay robustness, and competitive protein adsorption.

Size-controlled hexagonal- and cubic-phase NaYF4:Yb,Er nanocrystals with bright fluorescent emission were successfully synthesized via a solvothermal approach at a relatively low temperature (< 300 degrees C). A mixture of ethanol and ethylene glycol or pure ethylene glycol was used as a solvent, whereby changing the ethanol concentration. It is found that, besides reaction temperature and time, the reactant concentration is an important factor to control crystal phase. High reactant concentration, high reaction temperature, high concentration of ethanol and long reaction durations are favorable to the formation of brightly emitting hexagonal-phase nanocrystals. The effects of these reaction conditions on the size and the luminescent properties of the as-prepared nanocrystals are discussed. It is found that 30-120 nm hexagonal NaYF4:Yb,Er nanoparticles can be prepared using 0.04 M reactant concentration in 0-60% ethanol solution at 220 degrees C for 24 h.

The aim of this study was to investigate the use of triethyl phosphate (TEP) to regulate the hydrothermal crystallization of hydroxyapatite (HA) films onto Ti6Al4V substrates. The growth mechanism of the HA film and the development of [0001] HA crystallographic texture were studied. Films were crystallized in a 0.232 m Ca(NO3)2−0.232 m EDTA−0.187 m TEP−1.852 m KOH−H2O chemical system with a final isothermal temperature of 200 °C, and then evaluated at synthesis times from 0 to 46 h by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and X-ray pole figures. Thermodynamic phase stability diagrams were calculated to validate experimental findings. XRD, FESEM, TEM, and EDX results demonstrated the crystallization of a CaTiO3 film below 180 °C and a HA film above 180 °C. FESEM and X-ray pole figure analysis revealed a refinement of the orientation of the (0002) HA crystallographic plane and the c-axis o...

Highly dispersible silver nano-material was obtained by surface functionalization of silver nanoparticles with polylactic acid. The thiolation method was used for attaching carboxyl groups to the silver surface by treatment with 3-mercaptopropionic acid. The carboxyl groups were further activated by diisopropylcarbodiimide and reacted with polylactic acid. The functionalized nanoparticles contained 1.88 wt.% organic phase. While the as-received silver nanopowder exhibited poor colloidal stability in tetrahydrofuran, particle size analysis revealed that the functionalized material displayed high dispersibility in this solvent.

Calcium phosphate encapsulated silver powder was obtained by heterogeneous nucleation during treatments of dispersed silver first with solutions of Ca(NO 3 ) 2 and then with Na 2 HPO 4 . Before treatment silver powders were functionalized with 3-mercaptopropionic acid and dispersed in a precipitation medium so the carboxylate groups could serve as nucleation sites. The ratio Ca/P in the coating increases with the number of treatment cycles. In contrast, calcium phosphate precipitation by slow release of phosphate ions via hydrolysis of tri(4-nitrophenyl)phosphate in a solution of Ca(NO 3 ) 2 results in homogeneous nucleation only; coating does not form on silver particles.

As the field of nanotechnology continues to grow, evaluating the cytotoxicity of nanoparticles is important in furthering their application within biomedicine. Here, we report the synthesis, characterization, and cytotoxicity of nanoparticles of different morphologies of yttrium oxide, a promising material for biological imaging applications. Nanoparticles of spherical, rod-like, and platelet morphologies were synthesized via solvothermal and hydrothermal methods and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), light scattering, surface area analysis, thermogravimetric analysis (TGA), and zeta potential measurements. Nanoparticles were then tested for cytotoxicity with human foreskin fibroblast (HFF) cells, with the goal of elucidating nanoparticle characteristics that influence cytotoxicity. Cellular response was different for the different morphologies, with spherical particles exhibiting no cytotoxicity to HFF cells, rod-like particles increasing cell proliferation, and platelet particles markedly cytotoxic. However, due to differences in the nanoparticle chemistry as determined through the characterization techniques, it is difficult to attribute the cytotoxicity responses to the particle morphology. Rather, the cytotoxicity of the platelet sample appears due to the stabilizing ligand, oleylamine, which was present at higher levels in this sample. This study demonstrates the importance of nanoparticle chemistry on in vitro cytotoxicity, and highlights the general importance of thorough nanoparticle characterization as a prerequisite to understanding nanoparticle cytotoxicity.

The aim of this study was to investigate the use of Ca(EDTA)2− and triethyl phosphate (TEP) to regulate the hydrothermal crystallization of hydroxyapatite (HA) films. HA was coated on various substrates including titanium, Ti6Al4V, grit-blasted Ti6Al4V, 316 stainless steel, and Co28Cr6Mo via hydrothermal synthesis at 200 °C for 24 h utilizing a 0.232 molal Ca(NO3)2−0.232 molal EDTA−0.187 molal TEP−1.852 molal KOH−H2O chemical system. The role of film deposition processing variables on HA crystallization was studied using thermodynamic process simulation and experimental TEP hydrolysis kinetics data. Profilometry, XRD, FESEM, and adhesion testing (ASTM D3359) were used to characterize substrates and films. Kinetics studies of TEP hydrolysis revealed that phosphate was available for the formation of HA at temperatures above 180 °C and synthesis times greater than 4 h. Thermodynamic modeling demonstrated both that the formation of phase pure HA was thermodynamically favored at 200 °C on all substrates and th...

Interfacial reaction in a multiple emulsion, was carried out with the aim of preparing hollow hydroxyapatite (HAp) microspheres. The multiple emulsion was a W/O/W emulsion, made of dipotassium hydrogen phosphate solution as an inner aqueous phase, cyclohexane as an oil phase, and calcium nitrate solution as an outer aqueous phase. The phase diagrams of Ca(NO_3)2-K_2HPO_4-H_2O system were drawn by thermodynamic computations and used to simulate the chemical process in a multiple emulsion for determining the experimental conditions. Single phase HAp was synthesized at an initial pH of 12.0. HAp with a Ca/P ratio was measured by inductively coupled plasma spectroscopy to correspond to 1.49. The product was composed of microspheres of 0.5 to 2 μm in diameter. Each microsphere was composed of acicular particles with an aspect ratio of 2.5-10 with a short axis length of about 20 nm.

Increasing rare earth element (REE) supplies by recycling and expanded ore processing will result in generation of new wastewaters. In some cases, disposal to a sewage treatment plant may be favored, but plant performance must be maintained. To assess the potential effects of such wastewaters on biological treatment, model nitrifying organisms Nitrosomonas europaea and Nitrobacter winogradskyi were exposed to simulated wastewaters containing varying levels of yttrium or europium (10, 50, and 100 ppm), and the extractant tributyl phosphate (TBP, at 0.1 g/L). Y and Eu additions at 50 and 100 ppm inhibited N. europaea, even when virtually all of the REE was insoluble. Provision of TBP with Eu increased N. europaea inhibition, although TBP alone did not substantially alter activity. For N. winogradskyi cultures, Eu or Y additions at all tested levels induced significant inhibition, and nitrification shut down completely with TBP addition. REE solubility was calculated using the previously developed MSE (Mixed-Solvent Electrolyte) thermodynamic model. The model calculations reveal a strong pH dependence of solubility, typically controlled by the precipitation of REE hydroxides but also likely affected by the formation of unknown phosphate phases, which determined aqueous concentrations experienced by the microorganisms.

We report the design, calibration, and testing of a pre-clinical small animal imaging platform for use with short-wave infrared (SWIR) emitting contrast agents. Unlike materials emitting at visible or near-infrared wavelengths, SWIR-emitting agents require detection systems with sensitivity in the 1-2 μm wavelength region, beyond the range of commercially available small animal imagers. We used a collimated 980 nm laser beam to excite rare-earth-doped NaYF 4 :Er,Yb nanocomposites, as an example of a SWIR emitting material under development for biomedical imaging applications. This beam was raster scanned across the animal, with fluorescence in the 1550 nm wavelength region detected by an InGaAs area camera. Background adjustment and intensity non-uniformity corrections were applied in software. The final SWIR fluorescence image was overlaid onto a standard white-light image for registration of contrast agent uptake with respect to anatomical features.

The photoluminescent properties of the nanoscale rare earth ceramic clusters (THF) 14 Er 10 S 6 Se 12 I 6 (THF = tetrahydrofuran), (THF) 8 Nd 8 O 2 Se 2 (SePh) 16 , and the molecular thiolates (DME) 2 X(SC 6 F 5 ) 3 (DME = 1,2-dimethoxyethane, X = Er or Nd) are studied by optical absorption and photoluminescence. From the Judd–Ofelt (JO) analysis of the absorption spectra and the measured decay time of the photoemission it is found that the Er complexes show high quantum efficiencies whereas the Nd complexes not. The differences are explained in terms of energy transfer processes among the corresponding active ions. It is found that the Nd thiolate present the most drastic quenching in spite that the energy transfer processes are driven only by multipolar interactions whereas for the other complexes, there is evidence of migration for the Nd one and upconversion for the Er complex.

The synthesis of BaPbO3 from a wide range of mixtures containing metalorganic precursors, nitrate precursors, lead oxides, barium oxide and peroxide was investigated, and the kinetics was analyzed using the Johnson–Mehl–Avrami (JMA) equation. It was found that Ba and Pb stearate soaps and Pb oxalate that were used as metalorganic precursors formed BaCO3 and PbO or Pb3O4 after firing at 440 °C. The formation rate of BaPbO3 from a metalorganic precursor system is not higher than that from the conventional BaCO3–PbO system and does not depend on mixing methods or the kinds of metalorganic precursors but instead on the synthesis atmosphere. In the case of the BaCO3–PbO system, the Avrami exponent (n) is ∼1, indicating that the reaction is controlled by the phase-boundary-contraction interface reaction. For the BaO2–PbO2 system, n has two values ∼1 and ∼0.3, depending on the reaction temperature and time, indicating that the reaction is either controlled by the phase-boundary-contraction interface reaction or diffusion-controlled reaction. In the Ba nitrate–Pb nitrate system, phase-pure BaPbO3 is obtained at 550 °C, which is 250 °C lower than in the case of the BaCO3–PbO system. The value of n for the nitrate system is ∼1.5, indicating that the reaction is controlled by a three-dimensional (3D) diffusion-controlled nucleation mechanism. In the BaO–PbO system, the formation of BaPbO3 started at 350 °C by an exothermic reaction and the content of BaPbO3 in the product was ∼40 wt%, which is independent of reaction temperature as well as time in the temperature range of 350–500 °C.

Reactions of Ln(SePh)3 with SeO2 in THF give octanuclear oxoselenido clusters with the general formula (THF)8Ln8O2Se2(SePh)16 (Ln = Ce, Pr, Nd, Sm). In this isomorphous series, the eight Ln(III) ions are connected in the center by a pair of mu3-O2- ligands and mu5-Se2- ligands, with 14 bridging and two terminal selenolate ligands capping the cluster surface. Thermal decomposition at 700 degrees C of the Nd compound in vacuo led to the formation of a phase mixture of NdSe2, Nd2Se3, and Nd2O3. Near-IR emission experiments on the (THF)8Nd8O2Se2(SePh)16 and the fluorinated thiolate compound (DME)2Nd(SC6F5)3 demonstrate that clusters with oxo ligands are not only highly emissive, but also they emit at wavelengths not found in conventional oxides.

The influence of the hydrodynamic effects of fluid flow on the hydrothermal deposition of (001) oriented epitaxial Pb(Zr 0.7 Ti 0.3 )O 3 (PZT) thin films onto single-crystal SrTiO3 (100) substrates was investigated. The films were grown at 150 °C from lead acetate, zirconyl chloride, and titanium dioxide precursors and potassium hydroxide mineralizer under batch quiescent conditions and at varying stirring rates in the range of 200-1700 rpm. To ensure that the hydrodynamic effects of the stirring rate were not unique to a specific set of thermodynamic variables, two sets of reaction conditions were chosen corresponding to a precursor concentration of 0.3 m (Zr + Ti) and mineralizer concentrations of 6 and 10 m KOH. Thermodynamic computations predicted that the perovskite phase was stable at >99% yield under both sets of conditions. Characterization of the films by field-emission scanning electron microscopy, Rutherford backscattering, and X-ray diffraction showed that fluid flow derived from stirring significantly altered the microstructure, compositional homogeneity, phase purity, and crystal quality of the films. It was found that films deposited at higher stirring rates were thinner but also exhibited a higher degree of stoichiometry, phase purity, and epitaxy with the substrate. The study of the PZT film and particles growing simultaneously in the hydrothermal reactor provided useful insight into the crystallization mechanism. The mechanistic implications of these observations for the nucleation and growth of epitaxial films under hydrothermal conditions at low temperatures are discussed and related to mass transport effects, such as particle motion and chemical diffusion. A new crystallization mechanism is proposed based on particle encounters with a crystallizing surface and overlap of electrical double layers.

We demonstrated the formation of single-crystal-like materials that contain preferentially oriented arrays of lead zirconate titanate (PZT) cube-shaped particles by self-assembly. Hydrothermally synthesized PZT particles with a bulk composition of Zr/Ti = 70/30 were used in making microcrystal arrays. Spreading a suspension containing PZT cube-shaped particles, 2-propanol, and mineral oil at the air-water interface produced a one-dimensional planar array of PZT particles on the water surface. The array so formed was subsequently transferred onto a flat or curved substrate. X-ray diffraction and electron backscattered diffraction analyses revealed that most of the cube-shaped particles in the array were oriented with their pseudocubic (001) direction aligned parallel to the normal direction of the substrate surface. Filling the arrays with matrixes produced monolayer or multilayer textured composites. The piezoelectric properties of oriented cube-shaped micron-sized particles in the self-assembled arrays were measured using a modified atomic force microscope to reveal the ferroelectric nature of the PZT arrays.

Tetragonal barium titanate (BaTiO3) particles were synthesized at temperature as low as 220 °C through glycothermal reaction by using Ba(OH)2·8H2O and amorphous titanium hydrous gel as precursors and 1,4-butanediol and water as solvent. XRD, DSC and Raman data support that glycothermal processing method provides a simple low-temperature route for producing tetragonal BaTiO3 nanoparticles without alkaline mineralizers. It is also demonstrated that the size and shape of BaTiO3 particles can be controlled by reaction conditions such as reaction temperature and various volume ratio of 1,4-butanediol/water. This processing method can fabricate BaTiO3 powders with narrow size distribution and low aggregation. In addition, BaTiO3 nanopowder with a Ba/Ti atomic ratio of 1.000±0.003 can be obtained in a reproducible manner with glycothermal process.

A thermodynamic model was developed to describe the stability of (Ba,Sr)TiO 3 (BST) solid solutions in the Ba-Sr-Ti-K-(EDTA)-H 2 O (EDTA = ethylenediaminetetraacetic acid) system. Phase diagrams were computed to identify the range of conditions suitable for making phase-pure BST. Hydrothermal experiments were performed to validate the thermodynamic model. The model was found to be more useful when an ideal solid solution was used to estimate the energetics for the BST phase instead of experimental thermodynamic data. In addition, EDTA was found to promote stable conditions for BST formation. When attempting to prepare Ba 0.50 Sr 0.50 TiO 3 without EDTA, BaTiO 3 -rich and SrTiO 3 -rich phases precipitated separately, at 70°-160°C. However, in the presence of EDTA, a phase-pure Ba 0.55 Sr 0.45 TiO 3 solid solution was obtained at 90°-120°C. EDTA is effective because it prevents phase heterogeneities from forming and equalizes the adsorption affinity of strontium and barium species.

Thermodynamic modeling was utilized to identify reaction conditions to prepare phase-pure hydroxyapatite particulates (HA) by mechanochemical–hydrothermal (M–H) methods using Ca(OH)2 and (NH4)2HPO4 as precursors. The resulting HA powders were characterized by X-ray diffraction, infra-red spectroscopy, thermogravimetry, and transmission electron microscopy, nitrogen adsorption and dynamic light scattering methods. Choosing reaction conditions in the 99% yield region of the CaO–P2O5–NH4OH–H2O phase-pure equilibrium system, nearly stoichiometric and nanostructured HA powders were prepared at room temperature in as little as 1 h. The minimum time to obtain phase-pure HA was 8 h from the conventional attrition mill. As-prepared powders were found to be highly agglomerated with a mass-weighted mean diameter of 2.6 µm in deionized water and average agglomeration number (AAN) as high as 4.5 × 106. Dispersion studies revealed that the appropriate use of dispersants could reduce the mass-weighted mean diameter and AAN. In the presence of sodium polyacrylate, the mass-weighted mean diameter and AAN were 217 nm and 1600, respectively.

Thermodynamic modeling was used to predict the optimum synthesis conditions for precipitation of the phase-pure lead titanate (PbTiO 3 ) in the Pb–Ti-tetramethylammonium hydroxide (TMAH) system using a newly developed computer program for automatic generation of stability and yield diagrams. The thermodynamic model has been experimentally validated over a wide range of processing conditions. Like KOH-mineralized systems, it was determined that the pH of the hydrothermal reaction medium and the Pb/Ti ratio are critical factors in forming stoichiometric PbTiO 3 powder. Morphological evolution during the reaction suggests that the formation mechanism appears to be controlled by a dissolution and recrystallization process. Two possible growth mechanisms are proposed based on the magnitude of the Pb/Ti ratio. In the case of Pb/Ti ratio=1.1, at the early stage of the reaction (3 h) excess lead species promote the formation of spherical intermediate pyrochlore phase followed by the formation of primary cubic PbTiO 3 crystals. The growth of cubic PbTiO 3 crystals proceeds until the intermediate phase acting as a reservoir to provide precipitating ions is consumed. In case of Pb/Ti ratio=1.25, excess lead condition leads to the formation of a platelet-shaped intermediate pyrochlore phase. These platelet intermediate particles act as a template in which small cubic shaped PbTiO 3 grains grew on the surface of these platelets.

Barium titanate (BaTiO 3 ) nanoparticles were synthesized at the low temperature of 80°C through a glycothermal reaction using Ba(OH) 2 .8H 2 O and amorphous titanium hydrous gel as precursors and a solution of 1,4-butanediol and water as solvent. This processing method provides a simple low-temperature route for producing BaTiO 3 nanoparticles, which could also be extended to other systems. It is demonstrated that the size of BaTiO 3 particles can be controlled by reaction conditions, such as reaction temperature and various volume ratios of 1,4-butanediol/water.

An analysis technique was developed on the basis of a modified version of Sudduth's model for calculating maximum packing fraction (MPF). Calculated MPF values were compared with experimental values obtained with rheological methods. By analysis of MPF data for three commercial titania powders dispersed in low molecular weight polyethylene, a large difference was observed between the experimental and calculated MPF values. For instance, a TiO 2 P25/VF sample had an experimental MPF of 0.15 while the calculated value was ~0.8. To address this issue, f was incorporated as a variable that would influence the packing fraction. By studying the behavior of three different types of submicron titania, an empirical equation was devised, that correlated f with particle size, particle size distribution, and packing structure. This overall treatment appeared to be relevant for predicting the f for binary millimeter steel powder mixtures. Thus, the form of this empirical function may guide us towards developing a deri...

Dy3+- and Tm3+-doped lanthanum chloride was prepared via reactive atmosphere processing (RAP) of sol-gel derived hydroxide powders. The low-phonon energy chloride host facilitated the 1.3-μm emission from Dy3+ and the 1.2- and 1.4-μm emissions from Tm3+. The emission intensities of the Dy3+ and Tm3+ ions increased logarithmically with increasing RAP temperature. The dependence of emission intensities and lifetimes on the rare-earth (RE) concentration was also investigated. The emission intensity was found to increase up to 1 mole % RE for both ions. Luminescence quenching was observed for concentrations exceeding 1 mole % for Tm3+ and 0.1 mole % for Dy3+.

Amorphous Zr−Ti hydrous oxide submicrometer spheres were employed in hydrothermal syntheses of PbZr0.7Ti0.3O3heteroepitaxial thin films on single-crystal SrTiO3 substrates. Reactions utilizing processing variables that included precursor concentration (0.1−0.4 m), KOH concentration (6−12 m), and time (24−60 h) were carried out at 150 °C to evaluate the effect of this precursor on the formation of an epitaxial film. Selected experiments were also conducted to examine how this spherical precursor compares with two other precursor systems, that is, nanostructured amorphous Zr−Ti hydrous oxide prepared by coprecipitation at room temperature, and a mixture of crystalline TiO2 and amorphous ZrO2·nH2O obtained from soluble ZrOCl2·8H2O. On the basis of the results of X-ray diffraction and electron microscopy, precursor choice, precursor concentration, and KOH mineralizer concentration have a significant effect on the quality, composition, and morphology of the film.

Thermodynamic modeling of hydrothermal solutions was used to examine the influence of ethylenediamine tetra-acetic acid (EDTA) on the synthesis of lead-based perovskites, PbTiO3 and PbZr0.52Ti0.48O...

The hydrothermal synthesis of lead zirconate titanate (PZT) powder with acicular morphology using organic mineralizer, tetramethylammonium hydroxide pentahydrate (TMAH), has been investigated. The TMAH concentration and reaction time have a pronounced effect on the phase composition and morphology of the resultant powders. At 150°C phase pure PZT was obtained after 24 h in 0.5 m TMAH solution, and after 12 h in 1 m TMAH solution. TMAH concentrations lower than 0.5 m do not produce the PZT phase. At all TMAH concentrations, the appearance of a fibrous intermediate phase, Zr-modified tetragonal PX-phase PbTiO 3 is observed at the early stage of the hydrothermal process. Depending on the TMAH concentration, the intermediate either dissolves to form cube-shaped PZT (TMAH concentrations of 1–4 m) or transforms in situ to acicular PZT powder using its fibrous morphology as a template (TMAH concentrations of 0.5–0.75 m).

A thermodynamic model of electrolyte solutions has been used as a tool for equilibrium calculations in the Na−Bi−Ti−H2O and K−Bi−Ti−H2O systems. To perform the calculations, unknown standard-state properties for Na0.5Bi0.5TiO3 (NBT), K0.5Bi0.5TiO3 (KBT) and other solid compounds that exist in these systems were established. As a result of the calculations, stability and yield diagrams of the investigated systems were computed. Thus, the optimum conditions (i.e., temperature, synthesis precursor concentrations, solution pH) for the hydrothermal synthesis of phase-pure KBT and NBT are presented in a graphical form. They show the concentrations of precursors and pH-adjusting agents required for the formation of phase-pure alkaline bismuth titanates. The computed diagrams show that the formation of phase-pure sodium and potassium bismuth titanates takes place in highly alkaline solutions (e.g., at pH above 11.4 and 12.2, respectively, at 473 K). Results of our experiments validated the newly developed yield d...

Lead titanate was synthesized at 200°C from chelated titanium and lead in alkaline, aqueous solution. Complexing agents included H 2 O 2 and EDTA, with KOH and KF as mineralizers. After synthesis in hydrothermal autoclaves, the products were examined by field emission scanning electron microscopy (FESEM) and powder X-ray diffraction. Samples prepared with low Ti ( 1.2 m) concentrations were found to contain dendritic powder combined with a small fraction of square platelets varying in size from 50-200 μm. X-ray diffraction confirmed that the yellow powders were single-phase, tetragonal PbTiO 3 . The conditions under which these platelets were formed (200°C, 200 psi) are mild compared to conventional hydrothermal routes, which require > 500°C and > 10 000 psi to grow crystals of comparable size.

Hydrothermal research at the Rutgers University is focused on the preparation of multicomponent perovskite oxide compounds. Engineering principles are being developed by examining process thermodynamics and kinetics.

Using high temperature calorimetric techniques, enthalpies of mixing of melts, enthalpies of formation of glasses and enthalpies of formation of crystals have been measured in binary systems ZrF4-BaF2, ZrF4-NaF, ZrF4-LaF3 and selected compositions in the system ZrF4-BaF2-LaF3-AlF3-NaF. The system ZrF4-LaF3 shows essentially zero enthalpies of mixing of melts. In the other systems, there are strongly exothermic enthalpies of mixing. In the binary systems ZrF4-BaF2 and ZrF4-NaF, the enthalpy of mixing of melts and the enthalpy of formation of crystals show minima at the same compositions, Ba2ZrF8 and Na3ZrF7, respectively, indicating the stoichiometric complexes ZrF84− and ZrF73−. These results are discussed in relation to energetics, structure, speciation and acid-base chemistry and suggest the following: ZrF4, LaF3 and AlF3 are anionic complex-formers, while BaF2 and NaF are ionized in the molten state. The coordination number of the zirconium fluoride anionic complex varies with the amount of alkali or alkaline earth fluoride. A model is proposed in which glass-forming melts are dominated by ZrF5− species and lie near deep eutectics. Therefore, glass formation in fluorozirconates involves a substantial structural change, which is dominated by short-range atomic arrangements, from the melt with predominantly ZrF5− to the glass where zirconium is 7 or 8 coordinated by fluorine.

A comprehensive thermodynamic model has been applied to predict the optimum conditions for the hydrothermal synthesis of phase-pure strontium zirconate. The model is based on the accurate knowledge of standard-state thermochemical properties of all species and a realistic activity coefficient model. The predictions are conveniently summarized in the form of phase stability and yield diagrams. Unlike our previous works, the diagrams are automatically generated using newly developed software, which makes it possible to analyze the effect of reactant identity and concentrations, contaminants, pH, and temperature as independent variables. The calculations revealed a high sensitivity of the synthesis to the identity of Sr precursors, Sr/Zr molar ratio of starting materials, and temperature as well as to the contamination with carbonates. The predictions have been confirmed experimentally at two temperatures (433 and 473 K) using strontium hydroxide or strontium nitrate as sources of Sr and a hydrous zirconium ...

The sol–gel synthesis of fluoride materials provides a viable and low-cost method for achieving planar and bulk devices for integrated photonic applications. This paper describes these prospects and methods for the experimental development of patterned and waveguiding films. The sol–gel synthesis from both metal-organic and inorganic precursor systems is discussed in relation to their potential for passive and active device applications.