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1.
Transport of engineered nanoparticles in saturated porous media 总被引:3,自引:0,他引:3
Yuan Tian Bin Gao Carlos Silvera-Batista Kirk J. Ziegler 《Journal of nanoparticle research》2010,12(7):2371-2380
Engineered nanoparticles (NPs) can be released into soils as emerging groundwater contaminants because many of them show toxic
effects to the ecosystems; however, their fate and transport in soils are largely unknown. The present work examined the transport
behavior of two NPs, silver nanoparticles (AgNPs) and carbon nanotubes (CNTs), in saturated porous media. Sodium dodecylbenzene
sulfonate (SDBS), an anionic surfactant, was used to disperse the engineered NPs to enhance their stabilities in water. The
solubilized NPs were then applied to laboratory columns packed with two types of water-saturated quartz sand to obtain their
breakthrough curves. The experimental results showed that the surfactant-solubilized NPs were highly mobile in the saturated
porous media. The transport of CNTs in the column was similar to that of colloidal montmorillonite and their recovery rates
were around 100%. Less than 15% of the AgNPs were retained in the saturated column during the breakthrough experiments. However,
most of the retained AgNPs were released when a SDBS-free water pulse was used to flush the sand column. The Derjaguin–Landau–Verwey–Overbeek
(DLVO) theory and a colloid transport model were used to simulate the fate and transport of the engineered NPs in the sand
columns. The DLVO theory worked well with AgNPs, but failed to represent the interactions between CNTs and the two sand media.
Predictions of the transport model matched the experimental breakthrough data of the two engineered NPs well. Our results
indicate that theories and models of colloid transport in porous media may be applicable to describe the fate and behavior
of engineered NPs under certain circumstances. 相似文献
2.
Francesco Carlà Giulio Campo Claudio Sangregorio Andrea Caneschi César de Julián Fernández Lourdes I. Cabrera 《Journal of nanoparticle research》2013,15(8):1-16
Quantum dots (QDs) have received considerable attention due to their unique optical and electrical properties. Although substantial research has focused on the potential applications and toxicological impacts of QDs, far less effort has been directed toward understanding their fate and transport in the environment. In this work, the effect of four coatings, polyethylene glycol functionalized polymer (PEGP), carboxyl derivatized polymer (COOHP), linoleic acid (LA), and polyacrylic acid-octylamine (PAA-OA), on the transport and retention of QDs in porous media were evaluated under environmentally relevant conditions. Aqueous QD suspensions (ca. 10 nM) were introduced into water-saturated columns packed with 40–50 mesh Ottawa sand at a pore-water velocity of 7.6 m/day. At an ionic strength (IS) of 3 mM and pH of 7, PEGP-coated QDs were completely retained within the column, while more than 60 % of COOHP-coated QDs were transported through a column run under identical conditions. When PAA-OA and LA were used as coatings, effluent QD recoveries increased to more than 65 and 89 % of the injected mass, respectively. Additionally, a decrease in pH from 9.5 to 5.0, or an increase of IS from 0 to 30 mM reduced the eluted mass of PAA-OA-coated QDs by more than 2 and 15 times, respectively. The relative mobility of coated QDs (LA > PAA-OA > COOHP > PEGP) was consistent with total interaction energy profiles between QDs and sand surfaces calculated based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. At an IS of 3 mM (NaCl) and pH 7, a linear correlation was obtained between the fraction of eluted QDs and the magnitude of the primary interaction energy barrier. These findings demonstrate the strong dependence of QD transport on coating type and indicate that interaction energies based on DLVO theory can be used to predict the relative mobility of QDs in porous media. 相似文献
3.
Summary The results of an investigation about the heavy-metal distribution in pore waters of an estuarine shallow-water system (Cona
Marsh, Venice Lagoon) are described. The area was sampled for surface and subsurface sediments; pore waters were extracted
by centrifugation and heavy-metal concentration measured by means of PIXE technique. A high variability of heavy-metal concentration
was observed in pore waters of sampled sites, as a result of physico-chemical conditions in the water sediment column, with
a different spatial distribution between two groups of metals (Fe, Mn and Crvs. Cu, Ni and Zn). Concentration gradients between pore and bottom waters were evaluated in order to investigate the metal
enrichment as a function of their mobility in the sediment and diagenesis phenomena.
Paper presented at the IX Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 8–10, 1992, Rome. 相似文献
4.
Transport of surface-modified iron nanoparticle in porous media and application to arsenic(III) remediation 总被引:1,自引:0,他引:1
Sushil Raj Kanel Dhriti Nepal Bruce Manning Heechul Choi 《Journal of nanoparticle research》2007,9(5):725-735
The surface-modified iron nanoparticles (S-INP) were synthesized, characterized and tested for the remediation of arsenite
(As(III)), a well known toxic groundwater contaminant of concern. The S-INP material was fully dispersed in the aqueous phase
with a particle size distribution of 2–10 nm estimated from high-resolution transmission electron microscopy (HR-TEM). X-ray
photoelectron spectroscopy (XPS) revealed that an Fe(III) oxide surface film was present on S-INP in addition to the bulk
zero-valent Fe0 oxidation state. Transport of S-INP through porous media packed in 10 cm length column showed particle breakthroughs of 22.1,
47.4 and 60 pore volumes in glass beads, unbaked sand, and baked sand, respectively. Un-modified INP was immobile and aggregated
on porous media surfaces in the column inlet area. Results using S-INP pretreated 10 cm sand-packed columns containing ∼2 g
of S-INP showed that 100 % of As(III) was removed from influent solutions (flow rate 1.8 mL min−1) containing 0.2, 0.5 and 1.0 mg L−1 As(III) for 9, 7 and 4 days providing 23.3, 20.7 and 10.4 L of arsenic free water, respectively. In addition, it was found
that 100% of As(III) in 0.5 mg/L solution (flow rate 1.8 mL min−1) was removed by S-INP pretreated 50 cm sand packed column containing 12 g of S-INP for more than 2.5 months providing 194.4
L of arsenic free water. Field emission scanning electron microscopy (FE-SEM) showed S-INP had transformed to elongated, rod-like
shaped corrosion product particles after reaction with As(III) in the presence of sand. These results suggest that S-INP has
great potential to be used as a mobile, injectable reactive material for in-situ sandy groundwater aquifer treatment of As(III). 相似文献
5.
Isabella Nicotera Ameesh Khalfan Gabriel Goenaga Tao Zhang Andrew Bocarsly Steve Greenbaum 《Ionics》2008,14(3):243-253
Water and methanol transport behavior, morphology, and solvent adsorption of filler-free Nafion membrane, Nafion–SiO2, Nafion–TiO2, and two Nafion–Zr(HPO4)2 composites were investigated using nuclear magnetic resonance methods, including spin-lattice relaxation and pulsed-field-gradient
spin-echo diffusion conducted under both variable temperature and variable hydrostatic pressure conditions and scanning electron
microscopy analysis. A comparison between water and methanol self-diffusion coefficients reveals that the water mobility is
higher than the methanol mobility in all the membranes. Additionally, the inclusion of inorganic fillers improves both the
solvent uptakes and the transport properties of the composite membranes relative to filler-free Nafion, with the exception
of one of the Nafion–Zr(HPO4)2 composite. Nafion–Zr(HPO4)2 composites were prepared by two different procedures, in situ and ex situ. Although phosphorus-31 magic-angle spinning nuclear
magnetic resonance spectra show the same structures of the particles in both kinds of membranes, the morphology, solvent absorption
properties, and solvent mobilities are very different.
Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur Mer, Sept. 9–15, 2007. 相似文献
6.
Thin films of polymer electrolytes comprising of PVA and KOH (A) with and without the addition of zinc salts, viz., zinc acetate (B) and zinc triflate (C) as mixed cations were prepared via. solution casting method. The thermal stability and ionic conductivity of PVA–KOH solid
polymer electrolyte (A) were improved by the partial substitution of KOH with zinc salts. Among the two salts, zinc triflate was found to improve
both the physical as well as electrochemical properties of the PVA–KOH films more significantly than zinc acetate. An attempt
to optimize the ratio of various components of polymer electrolytes, viz., polymer: KOH: zinc salt was also made, based on
the dimensional stability and ionic conductivity values. Finally, the select category polymer film containing PVA–KOH–zinc
triflate (C) in an optimum ratio of 40:35:25 was deployed in coin cell fabrication and subjected to charge–discharge studies with a view
to demonstrate the possible electrochemical reversibility characteristics. Based on the encouraging results obtained from
the cycling study, C type films [PVA–KOH–zinc triflate] qualify themselves as potential polymer electrolytes for use in rechargeable Zn/AgO polymer
batteries. 相似文献
7.
Chin-Wei Wang Chun-Ming Wu Sunil K. Karna Chi-Yen Li Chien-Kang Hsu Carissa H. C. Li Wen-Hsien Li 《Journal of nanoparticle research》2011,13(8):3405-3412
We report on the observations of tunneling transport in nanocompacts, where nanoparticles are packed into compact units using
selective mass compositions and packing densities. An insulator-like thermal behavior in electron transport is seen in a very
loosely packed 6-nm Ag nanocompact, whereas the densely packed 4.5-nm Au nanocompact displays a metal-like thermal behavior.
Metal–insulator-like transitions, with the transition temperature can readily be tuned by controlling the bias voltage, are
observed in the nanocompact consists of mixtures of 2.4 nm Ag and 4.8 nm core/shell Cu/Cu2O nanoparticles. The resistivity across the metal–insulator transition is found to change by more than four orders-of-magnitude.
At low bias voltages or small excitation currents, the metal–insulator transition occurs at ~190 K. The transition temperature
can be tuned to reach the ambient temperature when a higher bias voltage or a larger current is allowed. Possible mechanisms
that may produce the observed transport characteristics in the nanocompacts are discussed. 相似文献
8.
Mg-doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Mg:Zn atomic ratio from 0
to 7%. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and magnesium acetate tetrahydrate were
heated under refluxing at 65 °C using methanol as a solvent. X-ray diffraction analysis reveals that the Mg-doped ZnO crystallizes
in a wurtzite structure with crystal size of 5–12 nm. These nanocrystals self-aggregated themselves into hollow spheres of
size of 800–1100 nm. High resolution transmission electron microscopy images show that each sphere is made up of numerous
nanoparticles of average diameter 5–11 nm. The XRD patterns, SEM and TEM micrographs of doping of Mg in ZnO confirmed the
formation of hollow spheres indicating that the Mg2+ is successfully substituted into the ZnO host structure of the Zn2+ site. Furthermore, the UV–Vis spectra and photoluminescence (PL) spectra of the ZnO nanoparticles were also investigated.
The band gap of the nanoparticles can be tuned in the range of 3.36–3.55 eV by the use of the dopants. 相似文献
9.
Developing of new generation optical polymeric pH sensors has increasing importance due to their stable structures. Available
polymeric sensors for different pH ranges are already needed. In the present study new kinds of monomeric and polymeric absorption
pH sensors (HBANP and PHBANP) derived from 2-amino-4-nitrophenol were prepared. The novel sensors were investigated in various
pH values using spectrophotometric, spectrofluorometric, and electrochemical techniques. The sensors showed sigmoidal correlations
vs. pH range in optical measurements. These correlations were improved as mathematical formula to obtain the solution pH.
HBANP and PHBANP differed from each other by response fields. HBANP had a sharp absorption increase between the pH of 6.5→7.5
while PHBANP spectrophotometrically responded at lower pHs. HBANP was colorless in acidic pHs, yellow-colored in neutral media
and red-colored in alkaline pHs. With its colorimetric responses in various pHs HBANP can be used to develop color-tunable
pH sensors. Electrochemical oxidation peak potentials and currents also particularly changed in various pHs. 相似文献
10.
Zhang Ye Hao Yuying Meng Weixin Xu Huixia Wang Hua Xu Bingshe 《Applied Physics A: Materials Science & Processing》2012,106(3):709-715
The electroplex between (2-(4-trifluoromethyl-2-hydroxyphenyl)benzothiazole) zinc [Zn(4-TfmBTZ)2] as an electron-acceptor and N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-biphenyl)-4,4′-diamine (NPB) as an electron-donor was
characterized by bilayer, blend, and multilayer quantum-well (MQW) device, respectively. The blend composition and quantum-well
number are effective parameters for tuning electroluminescence color. White light with high color purity and color rendering
index (CRI) was observed from these devices based on Zn(4-TfmBTZ)2/NPB. Moreover, the blend and MQW devices all exhibit high operation stability, hence excellent color stability. For the device
with 5 mol% NPB in blend layer, its Commission International Del’Eclairage (CIE) coordinate region is x=0.28–0.31, y=0.33–0.35 and CRI is 83.3–91.2 at 5–9 V. For MQW structure device with NPB of 60 nm thickness, its CIE coordinate region
is x=0.29–0.32, y=0.31–0.34 and CRI=87.9–92.5 at 10–15 V. Such high color stability and purity and CRI, being close to ideal white light, are
of current important for white OLED. 相似文献
11.
A. A. Zhukov V. K. Gartman D. N. Borisenko M. V. Chernysheva A. A. Eliseev 《Journal of Experimental and Theoretical Physics》2009,109(2):307-313
We report the results on measurements of the work function of carbon nanotubes and carbon-nanotube-based materials including
pristine multi-walled and single-walled carbon nanotubes as well as single-walled carbon nanotubes intercalated by CuI with
the Kelvin probe technique. We found the work function value 4.97–4.98 eV for pristine carbon nanotubes, while carbon nanotubes
infilled with CuI demonstrate the work function value decreased by more than 0.1 eV (4.86–4.96 eV). 相似文献
12.
Ying Wang Yinhua Li Zhengzhi Zhou Xihong Zu Yulin Deng 《Journal of nanoparticle research》2011,13(10):5193-5202
A series of nanostructured zinc compounds with different nanostructures such as nanobelts, flake-like, flower-like, and twinning
crystals was synthesized using zinc acetate (Zn(Ac)2) as a single-source. The evolution of the zinc compounds from layered basic zinc acetate (LBZA) to bilayered basic zinc acetate
(BLBZA) and twinned ZnO nano/microcrystal was studied. The low-angle X-ray diffraction spectra indicate the layered spacing
is 1.34 and 2.1 nm for LBZA and BLBZA, respectively. The Fourier transform infrared (FTIR) spectra results confirmed that
the bonding force of acetate anion with zinc cations decreases with the phase transformation from Zn(Ac)2 to BLBZA, and finally to LBZA. The OH− groups gradually replaced the acetate groups coordinated to the matrix zinc cation, and the acetate groups were released
completely. Finally, the Zn(OH)2 and ZnO were formed at high temperature. The conversion process from Zn(Ac)2 to ZnO with release of acetate anions can be described as Zn(Ac)2 → BLBZA → LBZA → Zn(OH)2 → ZnO. 相似文献
13.
Electrical, galvanomagnetic, and thermoelectric properties of PbSe in the void sublattice of opal 总被引:1,自引:0,他引:1
L. I. Arutyunyan V. N. Bogomolov D. A. Kurdyukov V. V. Popov A. V. Prokof’ev I. A. Smirnov 《Physics of the Solid State》1998,40(4):719-721
A study of transport phenomena, namely, electrical resistivity, thermopower, Hall coefficient, and magnetoresistance of p PbSe synthesized in opal voids has been carried out in the 4–300 K range. The parameters of the semiconducting material have
been determined at different void filling levels. An anomalous behavior of the hole mobility associated with surface scattering
from insulating opal-matrix walls has been observed.
Fiz. Tverd. Tela (St. Petersburg) 40, 781–783 (April 1998) 相似文献
14.
Charge distribution characteristics were investigated for nanoparticles synthesized in a diffusion flame aerosol reactor.
The nanoparticles considered were pristine TiO2 and Cu–TiO2, with Cu dopant concentrations ranging from 1 to 5 wt% with particle size from 25 to 60 nm. In situ measurements were conducted
by integrating a tandem differential mobility analyzer (TDMA) experimental setup with the flame aerosol reactor. A charging
model was used to identify the important parameters that govern the two charging mechanisms (diffusion and thermo-ionization)
in the flame and their relative importance at different operating parameters. The results indicate that TiO2 and Cu–TiO2 nanoparticles carry single as well as double unit charges. The charged fraction depends on particle size as well as on dopant
concentration. The charged fraction increased with increasing particle size and decreased with copper dopant concentration.
Measured charged fractions were similar for both the polarities at different mobility diameters. Based on the flame operating
parameters, the calculations indicate that diffusion charging is dominant in the flame, which is consistent with the experimental
results. 相似文献
15.
R. Eichhorn A. Ros J. Regtmeier T. Tu Duong P. Reimann D. Anselmetti 《The European physical journal. Special topics》2007,143(1):159-164
We report on a paradoxical migration mechanism in a microstructured
lab-on-a-chip environment.
The phenomenon is based on a subtle interplay between
Brownian motion (thermal noise), a periodic and symmetric microstructure,
and a biased AC electric field.
The resulting non-linear dynamics
far from thermal equilibrium gives rise to absolute negative
mobility, i.e. a migrational transport, which is – both for
negative and positive bias – always opposite to the net acting
force, in good agreement between experiment and theory. 相似文献
16.
The IR spectra and polarized Raman spectra of crystals of hexahydrates of zinc potassium and ammonium sulfates have been obtained
experimentally at 93 K and at room temperature. The frequencies and modes of normal vibrations of the octahedral complex [Zn(H2O)6]2+ have been calculated. The assignment of the observed lines of the internal and external vibrations of the crystal cell has
been made by calculations and by factor-group analysis.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 162–168, March–April, 2000. 相似文献
17.
The thermal behavior and transport properties of lead(II) tetrafluorostannate(II) have been investigated by impedance spectroscopy,19F NMR and high hydrostatic pressure techniques. It is shown that these experimental methods are powerful tools to clarify
ionic transport processes in the investigated solid electrolytes with predominant fluorine mobility.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
18.
An approach is presented, which allows determination of size and shape of subsurface low-contrast objects from their dielectric
properties and location of people and things present inside the buildings from the echo ultrabroadband electromagnetic signals.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 94–99, November, 2008. 相似文献
19.
Alena Reznickova Zdenka Kolska Vladimir Hnatowicz Vaclav Svorcik 《Journal of nanoparticle research》2011,13(7):2929-2938
Properties of pristine, plasma modified, and etched (by water and methanol) polytetrafluoroethylene (PTFE) were studied. Gold
nanolayers sputtered on this modified PTFE have been also investigated. Contact angle, measured by goniometry, was studied
as a function of plasma exposure and post-exposure aging times. Degradation of polymer chains was examined by etching of plasma
modified PTFE in water or methanol. The amount of ablated and etched layer was measured by gravimetry. In the next step the
pristine, plasma modified, and etched PTFE was sputtered with gold. Changes in surface morphology were observed using atomic
force microscopy. Chemical structure of modified polymers was characterized by X-ray photoelectron spectroscopy (XPS). Surface
chemistry of the samples was investigated by electrokinetic analysis. Sheet resistance of the gold layers was measured by
two-point technique. The contact angle of the plasma modified PTFE decreases with increasing exposure time. The PTFE amount,
ablated by the plasma treatment, increases with the plasma exposure time. XPS measurements proved that during the plasma treatment
the PTFE macromolecular chains are degraded and oxidized and new –C–O–C–, –C=O, and –O–C=O groups are created in modified
surface layer. Surface of the plasma modified PTFE is weakly soluble in methanol and intensively soluble in water. Zeta potential
and XPS shown dramatic changes in PTFE surface chemistry after the plasma exposure, water etching, and gold deposition. When
continuous gold layer is formed a rapid decrease of the sheet resistance of the gold layer is observed. 相似文献
20.
Safi Altunöz Hüseyin Çelik Mehmet Cankurtaran 《Central European Journal of Physics》2008,6(3):479-490
The mobility of electrons in vertical transport in GaAs/Ga1−y
Al
y
As barrier structures was investigated using geometric magnetoresistance measurements in the dark. The samples studied had
Ga1−y
Al
y
As (0 ≤ y ≤ 0:26) linearly graded barriers between the n+-GaAs contacts and the Ga0:74Al0:26As central barrier, which contain N
w
(=0, 2, 4, 7 and 10) n-doped GaAs quantum wells. The mobility was determined as functions of (i) temperature (80–290 K) at
low applied voltage (0.01–0.1 V) and (ii) applied voltage (0.005–1.6 V) at selected temperatures in the range 3.5–290 K. The
experimental results for the temperature dependence of low-field mobility suggest that space-charge scattering is dominant
in the samples with N
w
=0 and 2, whereas ionized impurity scattering is dominant in the samples with N
w
=4, 7 and 10. The effect of polar optical phonon scattering on the mobility becomes significant in all barrier structures
at temperatures above about 200 K. The difference between the measured mobility and the calculated total mobility in the samples
with N
w
=4, 7 and 10, observed above 200 K, is attributed to the reflection of electrons from well-barrier interfaces in the quantum
wells and interface roughness scattering. The rapid decrease of mobility with applied voltage at high voltages is explained
by intervalley scattering of hot electrons.
相似文献