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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Two-Color Emitting Colloidal Nanocrystals as Single-Particle Ratiometric Probes of Intracellular pH

Intracellular pH is a key parameter in many biological mechanisms and cell metabolism and is used to detect and monitor cancer formation and brain or heart diseases. pH-sensing is typically performed by fluorescence microscopy using pH-responsive dyes. Accuracy is limited by the need for quantifying the absolute emission intensity in living biological samples. An alternative with a higher sensitivity and precision uses probes with a ratiometric response arising from the different pH-sensitivity of two emission channels of a single emitter. Current ratiometric probes are complex constructs suffering from instability and cross-readout due to their broad emission spectra. Here, we overcome such limitations using a single-particle ratiometric pH probe based on dot-in-bulk CdSe/CdS nanocrystals (NCs). These nanostructures feature two fully-separated narrow emissions with different pH sensitivity arising from radiative recombination of core- and shell-localized excitons. The core emission is nearly independent of the pH, whereas the shell luminescence increases in the 3–11 pH range, resulting in a cross-readout-free ratiometric response as strong as 600%. In vitro microscopy demonstrates that the ratiometric response in biologic media resembles the precalibralation curve obtained through far-field titration experiments. The NCs show good biocompatibility, enabling us to monitor in real-time the pH in living cells.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Superior Fischer-Tropsch Performance of Uniform Cobalt Nanoparticles Deposited into Mesoporous SiC

Electrochemically-derived well-crystalline mesoporous silicon carbide (pSiC) was used to host cobalt nanoparticles and to show superior catalytic performance during the CO hydrogenation according to Fischer-Tropsch. Colloidal metal particles (9 ± 0.4 nm) were prepared independently before depositing them into pSiC and, for comparison purposes, into commercially available silica (Davisil) and foam-like MCF-17 supports. The Co/pSiC catalyst demonstrated the highest catalytic activity of 117 ?molCO gCo-1 s-1 at 220 °C in the Fischer-Tropsch reaction, while the silica supported cobalt samples showed about one order of magnitude less activity. A significant increase in the C5+ hydrocarbons selectivity for Co/pSiC was observed. The stable performance of the catalyst is attributed to the high dispersion of the active phase and the use of silicon carbide acting as a thermally conductive and chemically inert porous support.

lablokou, V. S.↗
DOE OSTI2023

Electrolytic Coagulant Generation for Treating Flowback and Produced Water for Reuse

This research investigated a novel electrochemical process for producing a ferric iron coagulant for use in treating flowback and produced water (FPW) from hydraulic fracturing and oil production operations. The electrolytic coagulant generation (ECG) system uses an electrochemical cell to produce acid and base from oilfield brine solutions. The acid is used to dissolve scrap iron to provide a Fe 3+ coagulating agent, and the base is used to neutralize the treated water. The costs for generating the ferric iron coagulant were determined as a function of current density and feed water salinity. The process was shown to be effective for removing colloidal bentonite particles from brine solutions. Here, the process has several advantages over conventional electrocoagulation using iron anodes, including: the ability to treat anoxic waters, elimination of electrode fouling, lower cost for the coagulant, and the ability to deliver Fe 3+ doses greater than 1 mM, since it is not limited by the amount of dissolved oxygen required to oxidize ferrous to ferric iron.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Recent Advances in Synthesis and Application of Lignin Nanoparticles

The ability to engineer material at its nanoscale has shown great potentials in overcoming significant obstacles in numerous fields. Because of its abundance, biodegradability, renewability, and eco-friendliness nature, lignin has become an ideal precursor for producing nanoscale materials from both research and industrial communities. Nanolignin, also known as colloidal lignin particle (CLP) or lignin nanoparticle (LNP), has received significant interest in recent years and its production and application in numerous fields represent an important aspect of lignin valorization. LNPs could be produced via several techniques including sonication, solvent exchange, and precipitation, which could be divided into wet and dry methods. Applications of LNPs in UV protection, cosmetics, food package, coatings, and drug delivery have been reported in the literature. Despite being extensively studied, LNPs as well as their derived materials with controlled shape and architecture are still largely underexploited. This book chapter mainly covers recent advances in the preparation of LNPs and their use in the novel and advanced applications in different areas.

Meng, Xianzhi↗
DOE OSTI2020

Self-Propulsion Enhances Polymerization

Self-assembly is a spontaneous process through which macroscopic structures are formed from basic microscopic constituents (e.g., molecules or colloids). By contrast, the formation of large biological molecules inside the cell (such as proteins or nucleic acids) is a process more akin to self-organization than to self-assembly, as it requires a constant supply of external energy. Recent studies have tried to merge self-assembly with self-organization by analyzing the assembly of self-propelled (or active) colloid-like particles whose motion is driven by a permanent source of energy. Here we present evidence that points to the fact that self-propulsion considerably enhances the assembly of polymers: self-propelled molecules are found to assemble faster into polymer-like structures than non self-propelled ones. The average polymer length increases towards a maximum as the self-propulsion force increases. Beyond this maximum, the average polymer length decreases due to the competition between bonding energy and disruptive forces that result from collisions. The assembly of active molecules might have promoted the formation of large pre-biotic polymers that could be the precursors of the informational polymers we observe nowadays.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1970

Diffusion filter eliminates fringe effects of coherent laser light source

Diffusion filter comprised of small particles in colloidal suspension reduces the coherence of a laser beam used as a photographic light source. Interference patterns which obscure details in photographic film are eliminated, the intensity and collimation are moderately affected.

Olsasky, M. J.↗
NASA NTRS1972

Insolubilized enzymes for food synthesis

Cellulose matrix with numerous enzyme-coated silica particles of colloidal size permanently bound at various sites within matrix was produced that has high activity and possesses requisite physical characteristics for filtration or column operations. Product also allows coupling step in synthesis of edible food to proceed under mild conditions.

Marshall, D. L.↗
NASA NTRS1971

An experimental facility for the visual study of turbulent flows.

An experimental technique which allows visual observations of the wall area in turbulent pipe flow is described in detail. It requires neither the introduction of any injection or measuring device into the flow nor the presence of a two-phase flow or of a non-Newtonian fluid. The technique involves suspending solid MgO particles of colloidal size in trichloroethylene and photographing their motions near the wall with a high speed movie camera moving with the flow. Trichloroethylene was chosen in order to eliminate the index of refraction problem in a curved wall. Evaluation of the technique including a discussion of limitations is included. Also the technique is compared with previous methods of visual observations of turbulent flow.

Brodkey, R. S.↗
NASA NTRS1990

The October 27-28, 1986, FIRE cirrus case study: Cloud microstructure

Using aircraft in-situ measurements, the microphysics of cirrus clouds observed on 28 Oct. 1986 during FIRE were examined. Results are presented as one component of a coordinated study of the cirrus on the day. The study contributes to the understanding of cold clouds by: (1) providing microphysical data to supplement satellite and aircraft data for investigating cirrus cloud radiative effects; (2) providing more complete information on ice particle evolution and cloud forcing mechanisms than has been available through the use of instrumentation with higher resolution and more accurate calibration; (3) expanding the knowledge of the particle characteristics in cold liquid water clouds, through improved instrumentation and by making use of sensors on other platforms, such as lidar; and (4) by estimating the ice nucleus concentrations active at low temperatures in the upper troposphere from the concentrations of ice particles in colloidally stable liquid water clouds.

Miller, Karen M.↗
NASA NTRS1990

The 27-28 October 1986 FIRE IFO cirrus case study - Cloud microstructure

Using aircraft in-situ measurements, the microphysics of cirrus clouds observed on 28 Oct. 1986 during FIRE were examined. Results are presented as one component of a coordinated study of the cirrus on the day. The study contributes to the understanding of cold clouds by: (1) providing microphysical data to supplement satellite and aircraft data for investigating cirrus cloud radiative effects; (2) providing more complete information on ice particle evolution and cloud forcing mechanisms than has been available through the use of instrumentation with higher resolution and more accurate calibration; (3) expanding the knowledge of the particle characteristics in cold liquid water clouds, through improved instrumentation and by making use of sensors on other platforms, such as lidar; and (4) by estimating the ice nucleus concentrations active at low temperatures in the upper troposphere from the concentrations of ice particles in colloidally stable liquid water clouds.

Heymsfield, Andrew J.↗
NASA NTRS1993

Graphite solubility and co-vesiculation in basalt-like melts at one-ATM

The identity and source of the vapor phase that caused lunar lava-fountaining and vesiculation in lunar basalts continues to be of interest because of its implications for the composition and state of the lunar interior and because of its implications for lunar resources. In light of the apparent near-absence of H2O on the Moon, it has been suggested that the vapor phase may be CO2-CO. This premise is supported by the presence of carbon on the surface of volcanic glass beads. However, although the rapid exsolution of CO2 from a melt during decompression may be consistent with firefountaining, it fails to provide a satisfying explanation for vesiculation in mare basalt where exsolution of the gas phase would more reasonably be related to cooling/crystallization at low pressure rather than decompression from high pressure. Also, geochemical trends in lunar volcanic glasses suggest that their source has an oxygen fugacity more reducing than the iron-wustite buffer, an oxygen fugacity that is inconsistent with presence of dissolved CO2-CO at depth. The results of experiments in which a vesicular 'basalt' is produced from a melt equilibrated with graphite and pure CO gas at one atmosphere pressure are reported. The vesiculation is apparently related to exsolution of CO or a CO species during cooling of the melt or growth of quench crystals. Additionally, particulate carbon dispersed through the quenched sample suggests that elemental carbon is either in solution in the melt prior to quenching or tends to go into suspension perhaps as colloid-like particles. These two observations may provide insight into the nature of fire-fountaining and vesiculation on the Moon.

Colson, R. O.↗
NASA NTRS2006

Stability Enhancement of Polymeric Sensing Films Using Fillers

Experiments have shown the stability enhancement of polymeric sensing films on mixing the polymer with colloidal filler particles (submicron-sized) of carbon black, silver, titanium dioxide, and fumed silicon dioxide. The polymer films are candidates for potential use as sensing media in micro/nano chemical sensor devices. The need for stability enhancement of polymer sensing films arises because such films have been found to exhibit unpredictable changes in sensing activity over time, which could result in a possible failure of the sensor device. The changes in the physical properties of a polymer sensing film caused by the sorption of a target molecule can be measured by any of several established transduction techniques: electrochemical, optical, calorimetric, or piezoelectric, for example. The transduction technique used in the current polymer stability experiments is based on piezoelectric principles using a quartz-crystal microbalance (QCM). The surface of the QCM is coated with the polymer, and the mass uptake by the polymer film causes a change in the oscillating frequency of the quartz crystal. The polymer used for the current study is ethyl cellulose. The polymer/ polymer composite solutions were prepared in 1,3 dioxolane solvent. The filler concentration was fixed at 10 weight percent for the composites. The polymer or polymer composite solutions were cast on the quartz crystal having a fundamental frequency of about 6 MHz. The coated crystal was subjected to a multistage drying process to remove all measurable traces of the solvent. In each experiment, the frequency of oscillation was measured while the QCM was exposed to clean, dry, flowing air for about 30 minutes, then to air containing a known concentration of isopropanol for about 30 minutes, then again to clean dry air for about 30 minutes, and so forth. This cycle of measurements for varying isopropanol concentrations was repeated at intervals for several months. The figure depicts some of the sensing film stability results for ethyl cellulose polymer, ethyl cellulose-carbon black, and ethyl cellulose-silicon dioxide composite systems. An ethyl cellulose film exhibited a marked decline in response in the first few months of study and settled to a steady average response after about four months. However, response varied widely around the average response for ethyl cellulose film. In contrast, ethyl cellulose- carbon black and ethyl cellulose-silicon dioxide composites also declined in the early months, but showed more repeatable sensing film activity after the initial decline. Similar trends were observed in experiments for ethyl cellulose-titanium dioxide and ethyl cellulose-silver composites.

Lin, Brian↗
DOE OSTI2016

Noble metal superparticles and methods of preparation thereof

A method comprises heating an aqueous solution of colloidal silver particles. A soluble noble metal halide salt is added to the aqueous solution which undergoes a redox reaction on a surface of the silver particles to form noble metal/silver halide SPs, noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs on the surface of the silver particles. The heat is maintained for a predetermined time to consume the silver particles and release the noble metal/silver halide SPs, the noble metal halide/silver halide SPs or the noble metal oxide/silver halide SPs into the aqueous solution. The aqueous solution is cooled. The noble metal/silver halide SPs, the noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs are separated from the aqueous solution. The method optionally includes adding a soluble halide salt to the aqueous solution.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Polydispersity on the Phase Diagram of Colloid Systems

A theoretical model is proposed that describes the experimentally observed phase diagram of colloidal dispersions of disk-shaped polydisperse particles. In the framework of the phenomenological theory of phase transitions, it is shown that if disk-shaped particles have polydispersity comparable in thickness and disk diameter, then the following sequence of phase transitions should be expected with increasing volume fraction of ϕ particles: an isotropic liquid (I); a nematic liquid crystal (N), in which the director n sets the preferred orientation of the disk normal; and the discotic (columnar) phase (C), in which the disklike molecules aggregate into liquid columns, and the latter form a two-dimensional hexagonal crystal consisting of liquid columns. However, when the particles forming the colloidal dispersion do not have any polydispersity in thickness (but the polydispersity in the particle diameter is preserved), another sequence of phase transitions takes place, in which the columnar phase is replaced by a smectic liquid crystal (S); that is, particles form a system of equidistant liquid layers. This work proposes and discusses the mechanisms of this behavior and new predictions that follow from this consideration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2000

Apparatus for electrohydrodynamically assembling patterned colloidal structures

A method apparatus is provided for electrophoretically depositing particles onto an electrode, and electrohydrodynamically assembling the particles into crystalline structures. Specifically, the present method and apparatus creates a current flowing through a solution to cause identically charged electrophoretically deposited colloidal particles to attract each other over very large distances (<5 particle diameters) on the surface of electrodes to form two-dimensional colloidal crystals. The attractive force can be created with both DC and AC fields and can modulated by adjusting either the field strength or frequency of the current. Modulating this lateral attraction between the particles causes the reversible formation of two-dimensional fluid and crystalline colloidal states on the electrode surface. Further manipulation allows for the formation of two or three-dimensional colloidal crystals, as well as more complex designed structures. Once the required structures are formed, these three-dimension colloidal crystals can be permanently frozen or glued by controlled coagulation induced by to the applied field to form a stable crystalline structure.

Trau, Mathias↗
NASA NTRS1999

Method for electrohydrodynamically assembling patterned colloidal structures

A method apparatus is provided for electrophoretically depositing particles onto an electrode, and electrohydrodynamically assembling the particles into crystalline structures. Specifically, the present method and apparatus creates a current flowing through a solution to cause identically charged electrophoretically deposited colloidal particles to attract each other over very large distances (<5 particle diameters) on the surface of electrodes to form two-dimensional colloidal crystals. The attractive force can be created with both DC and AC fields and can modulated by adjusting either the field strength or frequency of the current. Modulating this lateral attraction between the particles causes the reversible formation of two-dimensional fluid and crystalline colloidal states on the electrode surface. Further manipulation allows for the formation of two or three-dimensional colloidal crystals, as well as more complex designed structures. Once the required structures are formed, these three-dimension colloidal crystals can be permanently frozen or glued by controlled coagulation induced by to the applied field to form a stable crystalline structure.

Trau, Mathias↗