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1.
The adsorption of the cationic dye acridine orange (AO) by different monoionic laponites leads to changes in the colloid properties of this synthetic mineral in aqueous solutions. The organic cation is adsorbed by the mechanism of cation exchange. Small amounts of adsorbed dye keep the clay in a peptized state with all metallic cations. Greater amounts of AO result in the neutralization of the electric charge of the clay, and its flocculation. In excess AO the charge of the clay platelets becomes positive and the clay is peptized. The colloid properties are studied by absorbance curves in which the absorbance is described as a function of the degree of saturation with constant clay concentrations or with constant dye concentrations. In the absorbance curves three regions can be identified. The transition between the first and second or the second and third regions depend on the exchangeable metallic cation initially present in the clay. The spectrophotometric method is useful in identifying the presence of tactoids and flocculation mechanism, whether it results in card-house or in book-house flocs. 相似文献
2.
CHENG Mingming SUN Zhenying MA Wanhong CHEN Chuncheng ZHAO Jincai WANG Zhengping 《中国科学B辑(英文版)》2006,49(5)
The organic-inorganic layered solid catalyst Fe(bpy)32+-laponite was able to photodegrade Rhodamine B (RhB) by activation of dioxygen under visible irradiation (λ>420 nm), while the homogeneous aqueous solution Fe(bpy)32+ showed no photoactivity. The catalyst could be repeatedly used and retained its reactivity. The hybrid catalyst could be separated from the suspension by centrifugation or sedimentation. The TOC removal yield of RhB was measured. Reactive oxygen species (ROS) formed during degradation was detected by EPR. A possible mechanism was proposed on the basis of the experimental results. 相似文献
3.
R. De
Lisi G. Lazzara S. Milioto N. Muratore 《Journal of Thermal Analysis and Calorimetry》2007,87(1):61-67
Macromolecule/laponite nanomaterials were
studied by DSC and X-ray diffraction techniques. The matrices are poly(ethylene)
glycols at various molecular masses and poly(ethylene oxides)-poly(propylene
oxides)-poly(ethylene oxides) tri-block copolymers. The latter were tuned
by modulating the molecular masses, at constant hydrophilic/hydrophobic ratio,
and the hydrophilicity. For all the investigated systems, the enthalpy of
melting (ΔH
m)
is nearly constant up to a given composition thereafter it increases monotonically
reaching the value of the pure macromolecule. We proposed a model to interpret
the DSC data.
Briefly, it was invoked a mechanism of interaction
following which some segments of the adsorbed macromolecule are anchored to
the laponite (RD) particles and the remaining segments are radiating away
from the surface. The portion of the macromolecule in contact with RD does
not contribute to ΔH
m
whereas that radiating away from the clay does. Once that the RD surface is
saturated, the excess of the macromolecule behaves like the pure one. The
proposed model allowed to compute successfully the ΔH
m
values. The X-ray diffraction experiments ruled out the polymer intercalation
between the silicate sheets. 相似文献
4.
Synthesis of cation-exchanged laponite suspensions by laser ablation of microsized-metal particles in liquid 总被引:1,自引:0,他引:1
Laser ablation in the liquid technique has been used to synthesize cation-exchanged laponite suspensions. In summary, laser ablation of the microsize-metal powder (Co, Al, and Cu) dispersed in an aqueous solution containing deionized water laponite crystals was carried out using laser beam generated by a single-mode, Q-switched Nd-Yag laser operating at 532 nm with a pulse duration of 5.5 ns and 10 Hz repetition rate. Laser fluence was 0.265 J/cm2 for all tests. For all samples, the mass fraction of laponite was 1%. General observations of the prepared samples indicated that an aqueous suspension of 1 wt% laponite retained its free flowing liquid phase characteristics even after aging for several weeks. When bivalent cationic metals (Cu, Co, Al) were ablated in it for about 1 h, even with a small amount of the metal (0.025% and 0.050%) were generated, the suspension became highly viscous and behaved as a shear-thinning and thixotropic material. That is, the suspension gelled strongly when it was allowed to rest. The gels, however, could easily be reverted to a low viscosity liquid with simple shaking. Information from TEM and XRD analysis indicated that such a sol-gel transformation might be due to the charge exchange between the cationic species produced during the laser ablation and the sodium ions in the interlayers of the clay sheets. 相似文献
5.
6.
Nida Sheibat‐Othman Ana‐Maria Cenacchi‐Pereira Amilton Martins Dos Santos Elodie Bourgeat‐Lami 《Journal of polymer science. Part A, Polymer chemistry》2011,49(22):4771-4784
We report the kinetics and mechanism of soap‐free emulsion polymerization of styrene using laponite platelets as stabilizers. The polymerization was initiated by potassium persulfate and the latex particles were stabilized by laponite platelets dispersed in water. Laponite adsorption on the polymer particles was enhanced by the addition of poly(ethylene glycol) monomethylether methacrylate (PEGMA). Particle nucleation can be described using the classical homogeneous nucleation mechanism followed by coagulation of unstable precursors. Oligomeric radicals formed in the water phase become insoluble and precipitate on the laponite surface leading to primary precursor particles composed of a few polymer chains and one or several clay platelets. Mature latex particles are then generated by coagulation and growth of the previously formed precursor particles. Both the nucleation and initial aggregation rates increased in the presence of PEGMA. Calorimetric monitoring of the polymerization allowed estimating the heat produced by the reaction and the monomer conversion. Hence, using the monomer material balance, the number of radicals in the polymer particles could be estimated precisely. The average number of radicals per particle, $ \bar n $ , was found to be high in the range 3–6. This result was attributed to strong attractive interactions between the growing radicals and the clay surface. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
7.
8.
Cationic clays and Layered Double Hydroxides (LDHs) are both layeredion exchangers, in which a stable (micro)porosity can be induced via apillaring process. For the cationic clays, the [Zr]-pillaring of hectoritecreates a broad micropore distribution with the maximum at 1.42–2.12nm. The [Al]-equivalent exhibits a narrower distribution, with pores between0.71 and 1.06 nm being dominant. In case of the [Zr]-pillared form a surfacearea of 294 m2/g and a micropore volume of 0.118cm3/g have been obtained. The same reaction on the syntheticlaponite clay reveals a much higher surface area (606 m2/g)and porosity (µPV = 0.336 cm3/g). Forlaponite, extra pores are created in the supermicropore-small mesoporeregion due to the preferential edge-to-face and edge-to-edge stacking of itssmaller sized clay layers.For the pillaring of MgAl- and ZnAl-LDHs with polyoxometalates (POMs),using large organic anions for pre-swelling purposes forms the mostpromising method for the creation of stable pores. It avoids the formationof sidephases, and gives rise to medium(-high) µPVs. Charge density onthe layers forms the key factor, lowering it improves the porositycharacteristics significantly. [Fe(CN)6]-MgAl-LDHs exhibitmore spectacular properties, with surface areas and µPVs exceedingthose of pillared hectorite. A variation in the charge density via theM
II/M
III ratio optimizes theporosity properties. A M
II/M
IIIratio of 3.33 results in a SA of 499 m2/g and a µPV of0.177 cc/g. For LDHs, both types of pillars create mainly small micropores,with a diameter smaller than 0.71 nm. 相似文献
9.
Norma Negrete‐Herrera Jean‐Luc Putaux Laurent David Felix De Haas Elodie Bourgeat‐Lami 《Macromolecular rapid communications》2007,28(15):1567-1573
Transparent film materials with excellent mechanical and thermal properties were elaborated by drying a latex suspension of armored polymer/Laponite composite particles. Low‐temperature TEM observation of ultrathin cross‐sections of the films indicated a unique network morphology characterized by a “honeycomb” distribution of the Laponite platelets remindful of the original particles morphology.
10.
Tingting Jiang Changchang Zhang Dr. Wenjie Sun Prof. Xueyan Cao Dr. Goeun Choi Prof. Jin-Ho Choy Prof. Xiangyang Shi Prof. Rui Guo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(11):2470-2477
Multidrug resistance (MDR) is regarded as a main obstacle for effective chemotherapy, and P-glycoprotein (P-gp)-mediated drug efflux has been demonstrated to be the key factor responsible for MDR. In this study, a novel pH-responsive hybrid drug delivery system was developed by conjugating d -α-tocopheryl polyethylene glycol 1000 succinate (TPGS), a kind of P-gp inhibitor, on the surface of laponite nanodisks to overcome MDR. The prepared LM-TPGS display excellent colloidal stability, a high encapsulation efficiency of doxorubicin (DOX), and a pH-responsive drug release profile. In vitro experiments verified that LM-TPGS/DOX could exhibit significantly enhanced therapeutic efficacy in treating DOX-resistant breast cancer cells (MCF-7/ADR) through inhibiting the activity of P-gp-mediated drug efflux and effectively accumulating DOX within cancer cells. In vivo results revealed that LM-TPGS/DOX outstandingly suppressed MCF-7/ADR tumors with low side effects. Therefore, the high drug payload, enhanced inhibition efficacy to drug-resistant cells, and low side effects make the LM-TPGS/DOX a promising nanoplatform to reverse MDR for effective chemotherapy. 相似文献