Articoli di riviste: "Surface complexation structure"

1

Maldonado-Valderrama, Julia, Yan Yang, Maykel Jiménez-Guerra, Teresa del Castillo-Santaella, José Ramos e Alberto Martín-Molina. "Complexation of DNA with Thermoresponsive Charged Microgels: Role of Swelling State and Electrostatics". Gels 8, n. 3 (17 marzo 2022): 184. http://dx.doi.org/10.3390/gels8030184.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Micro- and nanogels are being increasingly used to encapsulate bioactive compounds. Their soft structure allows large loading capacity while their stimuli responsiveness makes them extremely versatile. In this work, the complexation of DNA with thermoresponsive microgels is presented. To this end, PEGylated charged microgels based on poly-N-isopropylacrylamide have been synthesized, allowing one to explore the electrostatics of the complexation. Cationic microgels complexate spontaneously by electrostatic attraction to oppositely charged DNA as demonstrated by electrophoretic mobility of the complexes. Then, Langmuir monolayers reveal an increased interaction of DNA with swollen microgels (20 °C). Anionic microgels require the presence of multivalent cations (Ca2+) to promote the complexation, overcoming the electrostatic repulsion with negatively charged DNA. Then again, Langmuir monolayers evidence their complexation at the surface. However, the presence of Ca2+ seems to induce profound changes in the interaction and surface conformation of anionic microgels. These alterations are further explored by measuring adsorbed films with the pendant drop technique. Conformational changes induced by Ca2+ on the structure of the microgel can ultimately affect the complexation with DNA and should be considered in the design. The combination of microstructural and surface properties for microgels offers a new perspective into complexation of DNA with soft particles with biomedical applications.

2

Sun, Yubing, Xiangxue Wang, Wencheng Song, Songhua Lu, Changlun Chen e Xiangke Wang. "Retracted Article: Mechanistic insights into the decontamination of Th(iv) on graphene oxide-based composites by EXAFS and modeling techniques". Environmental Science: Nano 4, n. 1 (2017): 222–32. http://dx.doi.org/10.1039/c6en00470a.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Varadachari, Chandrika, Tarit Chattopadhyay e Kunal Ghosh. "The crystallo-chemistry of oxide-humus complexes". Soil Research 38, n. 4 (2000): 789. http://dx.doi.org/10.1071/sr99053.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Complexation of humic substances with goethite, hematite, gibbsite, and boehmite has been explained from a viewpoint of crystal structure of the minerals. Theoretical analysis of crystal surface structures revealed the following. (i) Residual charge carried by O or OH on surfaces of gibbsite is –1/2; on boehmite it is –3/2 or –1/2; on goethite it is –4/3, –2/3, or –1/3; and on hematite it is –3/2, –1, or –1/2. Cations adsorbed to neutralise these charges can form bridging links with humic acid; higher charges form stronger links. (ii) Surfaces of goethite, hematite, and gibbsite also contain octahedral sites in which one O/OH position is vacant. These may provide centres for the formation of strong coordination bonds. (iii) Such vacant octahedral positions are absent in boehmite. It follows that in gibbsite, cation bridging links would be weak and vacant octahedral sites would be the dominant bonding sites; in goethite and hematite, both cation bridging and surface coordination sites would be present; in boehmite, cation bridging would be the only strong bonding mode. Derivations from crystallochemical analysis are supported by experimental observations. Infrared studies also show strong OH involvement in boehmite complexation in contrast to the weakness of OH involvement in gibbsite complexes.

4

Hiemstra, Tjisse, Rasoul Rahnemaie e Willem H. van Riemsdijk. "Surface complexation of carbonate on goethite: IR spectroscopy, structure and charge distribution". Journal of Colloid and Interface Science 278, n. 2 (ottobre 2004): 282–90. http://dx.doi.org/10.1016/j.jcis.2004.06.014.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

5

TIWARY, AMIT S., PARTHA SARATHI SENGUPTA e ASOK K. MUKHERJEE. "MODELING THE GROUND STATE GEOMETRY AND ESTIMATING THE CHARGE TRANSFER TRANSITION ENERGY OF THE TOLUENE–ICl MOLECULAR COMPLEX BY AB INITIO AND DFT METHODS". Journal of Theoretical and Computational Chemistry 07, n. 03 (giugno 2008): 331–46. http://dx.doi.org/10.1142/s0219633608003782.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Out of several plausible isomeric structures of the toluene–ICl charge transfer (CT) complex, the most feasible one was determined by a detailed ab initio and DFT study at the HF, B3LYP, and mPW1PW91 levels using 6-31++G(d, p) basis set. Potential energy surface scans were performed with six possible structures ( I and Cl facing the o-, m-, and p-carbon atoms of toluene separately); the structures at the local minima of the surfaces were subjected to frequency calculation and the ones having no negative frequency were accepted as the real structure in the ground state. These structures were then subjected to full optimization. It was observed that the I – Cl bond, with its I atom oriented toward the aromatic ring, stands vertically above a C -atom at the ortho or para positions, being inclined at about 9° to the line perpendicular to the aromatic ring. Complexation increases the I – Cl bond length. After correction for basis set superposition error through a counterpoise calculation, we conclude from the binding energy that the preferred structure is the one with ICl above the ortho C atom. The calculated binding energy closely matches the experimental free energy of complexation. The electronic CT transition energy (hν CT ) with this structure in the ground state was calculated in vacuo by the restricted configuration interaction singlets method and in carbontetrachloride medium by the time dependent density functional theory method under the polarizable continuum model. The value of hν CT obtained from the ground-to-excited state transition electric dipole moments of the complex, is close to (somewhat underestimated) the reported experimental value.

6

Zimmermann, C. J., N. Ryde, N. Kallay, R. E. Partch e E. Matijević. "Plasma modification of polyvinyltoluene and polystyrene latices". Journal of Materials Research 6, n. 4 (aprile 1991): 855–60. http://dx.doi.org/10.1557/jmr.1991.0855.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Polyvinyltoluene (PVT) latex particles were etched with O2 or CF4/O2 plasma and polystyrene (PS) latex by the O2 plasma. While the effect of these treatments on the surface topology and the specific surface area was minor, the electrokinetic measurements showed a significant change in the surface charge characteristics. The interpretation of the results in terms of a surface complexation model, taking the Stern–Gouy–Chapman structure of the interfacial layer into consideration, yielded the values of the corresponding equilibrium constants, which indicated that the chemical nature and the density of the surface charged groups were altered by plasma attacks.

7

de Jonge, L. W., P. Moldrup e P. Schjønning. "Soil Infrastructure, Interfaces and Translocation Processes in Inner Space (''Soil-it-is''): towards a road map for the constraints and crossroads of soil architecture and biophysical processes". Hydrology and Earth System Sciences Discussions 6, n. 2 (25 marzo 2009): 2633–78. http://dx.doi.org/10.5194/hessd-6-2633-2009.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Abstract. Soil functions and their impact on health, economy and the environment are evident at the macro scale but determined at the micro scale, based on interactions between soil micro-architecture and the transport and transformation processes occurring in the pore and particle networks and at their interfaces. Soil structure formation and its resilience to disturbance are highly dynamic features affected by management (energy input), moisture (matric potential), and solids composition and complexation (organic carbon, OC, and clay interactions). In this paper we review and put into perspective preliminary results of the newly started research program ''Soil-it-is'' on functional soil architecture. To identify and quantify biophysical constraints on soil structure changes and resilience, we claim that new paradigms are needed to better interpret processes and parameters measured at the bulk soil scale and their links to the seemingly chaotic soil inner space behavior at the micro scale (soil self-organization). As a first step, we revisit the soil matrix (solids phase) and pore system (water and air phases), constituting the complementary and interactive networks of soil infrastructure. For a field-pair with contrasting soil management, we suggest new ways of data analysis on measured soil-gas transport parameters at different moisture conditions to evaluate controls of soil matrix and pore network formation. Results imply that some soils form sponge-like pore networks (mostly healthy soils in terms of environmental functions), while other soils form pipe-like structures (poorly functioning soils), with the difference related to both complexation of organic matter and degradation of soil structure. The recently presented Dexter threshold (ratio of clay to organic carbon of 10 g g−1) is found to be a promising constraint for a soil's ability to maintain or regenerate functional structure. Next, we show the Dexter threshold may also apply to hydrological and physical-chemical interface phenomena including soil-water repellency and sorption of volatile organic vapors (gas-water-solids interfaces) as well as polycyclic aromatic hydrocarbons (water-solids interfaces). However, data for differently-managed soils imply that energy input, soil-moisture status, and vegetation (quality of eluded organic matter) may be equally important constraints together with the complexation and degradation of organic carbon in deciding functional soil architecture and interface processes. Finally, we envision a road map to soil inner space where we search for the main controls of particle and pore network changes and structure build-up and resilience at each crossroad of biophysical parameters, where, for example, complexation between organic matter and clay, and moisture-induced changes from hydrophilic to hydrophobic surface conditions can play a role. We hypothesize that each crossroad (e.g. between OC/clay ratio and matric potential) may initiate breakdown or activation of soil self-organization at a given time as affected by gradients in energy and moisture from soil use and climate. The road map may serve as inspiration for renewed and multi-disciplinary focus on functional soil architecture.

8

Son, Yeongkyun, Tae-Hyun Kim, Daekeun Kim e Yuhoon Hwang. "Porous Clay Heterostructure with Alginate Encapsulation for Toluene Removal". Nanomaterials 11, n. 2 (3 febbraio 2021): 388. http://dx.doi.org/10.3390/nano11020388.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

A volatile organic compound adsorbent based on a porous clay heterostructure (PCH) with alginate biopolymer was successfully prepared. From N2 adsorption–desorption analysis, the specific surface area, pore volume, and pore size of bentonite were dramatically increased after introducing the porous structure. Following complexation with alginate (Alg-PCH), the pore volume and pore size were not significantly affected by pore structure. The thermal stability of Alg-PCH shows enhanced thermal stability compared to alginate and alginate beads. The morphology layered structure of Alg-PCH was carried out by transmission electron microscopy (TEM), suggesting the disorder and re-order of the c-axis layer stacking by porous structure and complexation with alginate, respectively, which was well-matched with X-ray diffraction results. To optimize the preparation of Alg-PCH, various reaction conditions (alginate, CaCl2 concentration, bead size, and weight ratio between alginate and PCH) were utilized. According to the toluene adsorption–desorption experiments, the preparation conditions for Alg-PCH were selected as a 2 mm extrusion tip, 0.5% of alginate, and 2% of CaCl2 solution with a 1:50 alginate:PCH weight ratio. Additionally, it shows 61.63 mg/g adsorption capacity with around 49% desorption efficacy under atmospheric temperature and pressure.

9

Larsson, Maja A., Ingmar Persson, Carin Sjöstedt e Jon Petter Gustafsson. "Vanadate complexation to ferrihydrite: X-ray absorption spectroscopy and CD-MUSIC modelling". Environmental Chemistry 14, n. 3 (2017): 141. http://dx.doi.org/10.1071/en16174.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Environmental contextVanadium, a metal pollutant from fossil fuels and slags, may be toxic, thereby necessitating an understanding of its environmental chemistry. One important factor that controls the mobility and bioavailability of vanadium is its binding to iron oxides. This study focuses on the characterization and modelling of vanadium adsorption onto ferrihydrite. The new model can be used to simulate the transport and bioavailability of vanadium in the environment. AbstractThe mobility of vanadium in the environment is influenced by sorption to metal (hydr)oxides, especially those containing iron. The aim of this study is to understand the adsorption behaviour of vanadium on poorly ordered (two-line) ferrihydrite (Fh). A further objective was to determine the binding mechanism of vanadate(V) to ferrihydrite surfaces in aqueous suspension to constrain the CD-MUSIC surface complexation model. Vanadium adsorption to ferrihydrite was evaluated by batch experiments which included series with different Fh-to-V ratios and pH values. Vanadate(V) adsorption was also evaluated in the presence of phosphate to compete with vanadate(V) for the available surface sites on ferrihydrite. In agreement with earlier studies, vanadate(V) was strongly adsorbed to ferrihydrite and the adsorption increased with decreasing pH. In the presence of phosphate, less vanadate(V) was adsorbed. Analysis by X-ray absorption near-edge structure spectroscopy revealed that the adsorbed vanadium was tetrahedral vanadate(V), VO4, regardless of whether vanadate(V) or vanadyl(IV) was added to the system. Spectra collected by extended X-ray absorption fine structure spectroscopy showed that vanadate(V) is bound primarily as an edge-sharing bidentate complex with V⋯Fe distances around 2.8Å. Based on this information, a surface complexation model was set up in which three bidentate vanadate(V) complexes with different degrees of protonation were included. The model provided a satisfactory description of vanadate(V) adsorption over most of the pH and concentration ranges studied, also in the presence of competing phosphate ions.

10

Colin-Garcia, M., A. Heredia, A. Negron-Mendoza, F. Ortega, T. Pi e S. Ramos-Bernal. "Adsorption of HCN onto sodium montmorillonite dependent on the pH as a component to chemical evolution". International Journal of Astrobiology 13, n. 4 (12 maggio 2014): 310–18. http://dx.doi.org/10.1017/s1473550414000111.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

AbstractThe aim of this work is to study the behaviour of hydrogen cyanide (HCN) adsorbed onto mineral surfaces (sodium montmorillonite, a clay mineral) in different pH environments as a possible prebiotic process for complexation of organics. Our experimental results show that specific sites on the surface of the clay increased the concentration of HCN molecules dependent on the pH values. Moreover, this adsorption can occur through physical and chemical interactions enhanced by the channel structure of the sodium montmorillonite. The three-dimensional channelling structure of the clay accumulates the organics, hindering the releasing (desorption) of the organic molecules. A molecular model developed here also confirms the role of the pH as a regulating factor in the adsorption of HCN onto the inorganic surfaces and the possibility for further reactions forming more complex molecules, as an abiotic mechanism important in prebiotic chemical evolution processes.

11

Gu, Zhiqiang, Qi Zhang, Guobi Sun, Jiaxin Lu, Yuxin Liu, Zhenxia Huang, Shuming Xu, Jianghua Xiong e Yuhuan Liu. "Pretreatment of Biogas Slurry by Modified Biochars to Promote High-Value Treatment of Wastewater by Microalgae". Sustainability 15, n. 4 (9 febbraio 2023): 3153. http://dx.doi.org/10.3390/su15043153.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

High concentrations of contaminants such as ammonia nitrogen and organic matter in full-strength wastewater severely inhibit the growth of microalgae, contributing to lower biomass accumulation and contaminant removal efficiency. To overcome this limitation, modified biochars prepared from pine sawdust and sugarcane bagasse were used in this study as an adsorbent–desorbent for the pretreatment of wastewater to promote the growth of microalgae. The results showed that the two modification methods (acid/alkaline modification and magnesium salt modification) used in the experiment could increase the abundance of oxygen-containing functional groups. Moreover, magnesium salt modification could effectively improve the pore structure of biochar surfaces and increase the specific surface areas. Compared with the pristine biochars, the adsorption performance of the modified biochar was found to be significantly higher for nutrients in wastewater. The adsorption capacity of the acid/alkaline-modified pine sawdust biochar reached 8.5 and 16.49 mg∙g−1 for ammonia nitrogen and total organic carbon in wastewater, respectively. The magnesium salt modified pine sawdust biochar achieved a more comprehensive nutrients adsorption capacity of 15.68, 14.39, and 3.68 mg∙L−1 for ammonia nitrogen, total organic carbon, and total phosphorus, respectively. The mechanism of ammonia nitrogen adsorption was mainly the complexation of surface -OH functional groups, while the adsorption mechanism for phosphate was mainly the complexation of -OH and Mg-O functional groups and the chemical precipitation of MgO or Mg(OH)2 attached to the surface.

12

Issaoui, Chokri, Hammouda Chebbi, Khaled Alouani e Abderrahmen Guesmi. "Crystal structure and Hirshfeld surface analysis of the new cyclodiphosphazane [EtNP(S)NMe2]2". Acta Crystallographica Section E Crystallographic Communications 73, n. 5 (11 aprile 2017): 682–86. http://dx.doi.org/10.1107/s2056989017005187.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

The cyclic compound 2,4-bis(dimethylamino)-1,3-diethylcyclodiphosphazane-2,4-dithione [systematic name: 2,4-bis(dimethylamino)-1,3-diethyl-1,3,2λ5,4λ5-diazadiphosphetidine-2,4-dithione], C8H22N4P2S2or [EtNP(S)NMe2]2, is member of a class of molecules that may be used, by virtue of their complexation properties, for the extraction of metals. This compound was characterized in solution by (1H and31P) NMR, and in the solid state by energy-dispersive X-ray spectroscopy (EDX) and by X-ray crystallography. In the crystal, the molecule sits on an inversion centre such that the P and N atoms form a centrosymmetric cyclic P2N2arrangement. The crystal packing is dominated by van der Waals interactions. The prevalence of these interactions is illustrated by an analysis of the three-dimensional Hirshfeld surface (HS) and by two-dimensional fingerprint plots (FP). The relative contribution of different interactions to the HS indicates that the H...H contacts account for 74.3% of the total HS area.

13

Niu, Huiqun, Hongying Yang e Linlin Tong. "Structural Characterization and Adsorption Capability of Carbonaceous Matters Extracted from Carbonaceous Gold Concentrate". Minerals 11, n. 1 (28 dicembre 2020): 23. http://dx.doi.org/10.3390/min11010023.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

In this paper, the structures of element carbon and humic acid extracted from carbonaceous gold concentrate were characterized employing a variety of analytical methods. The extracted amounts of ECE (elemental carbon extract) and HAE (humic acid extract) were 14.84–38.50 and 11.55–28.05 mg g−1, respectively. SEM and porosity analysis indicated that ECE occurred mostly as irregular blocky particles with a mesoporous surface with the average pore diameter being 31.42 nm. The particle size of ECE was mainly ranged from 5.5 to 42 μm and the specific surface area was 20.35 m2 g−1. The physicochemical features and structure of ECE were close to activated carbon, and the crystallinity was slightly lower than graphite. The particle size distribution of HAE varied from 40 to 400 nm with the specific surface area of 42.84 m2 g−1, whereas the average pore diameter of HAE was 2.97 nm. FTIR and UV–VIS analyses indicated that HAE was a complex organic compound containing the enrichment of oxygen-containing structure. The results showed that the adsorption amounts of ECE and HAE under the acidic conditions were 470.46 and 357.60 mg g−1, respectively. In an alkaline environment, the amount of ECE was 449.02 mg g−1 and the value of HAE was 294.72 mg g−1. ECE mainly utilized the outer surface and mesoporous structure to adsorb gold, while the functional groups’ complexation or surface site adsorption was the leading approach for HAE to adsorb gold.

14

SHIN, DONG-MYUNG, DONG-MEE SONG, GEEWON CHUNG e KYEONGTAE KIM. "COMPLEXATION OF AROMATIC MOLECULES WITH NEW CALIXARENE DERIVATIVES CONTAINING TWO ARYL SULFIDE RINGS". Journal of Nonlinear Optical Physics & Materials 14, n. 04 (dicembre 2005): 513–20. http://dx.doi.org/10.1142/s0218863505002967.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

The cuplike structure of calix[4]arenes is one of the most attractive features, which has been observed both in the solid state and in solution. The newly synthesized 5,11,17,23-tetrakis(3-mercaptopropyl)calix[4]arene (1) and 25,26,27,28-tetrakis(5-mercaptopenthoxy)calix[4]arene containing aryl sulfide rings (2), have four alkyl thiol linkages, which allow the calixarenes to attach onto the gold surface. Surface plasmon resonance (SPR) spectroscopy allows us to monitor the binding of calixarene derivatives on the gold surface. The 1 and 2 bind very effectively on the gold surface and self-assembled layers of 1 and 2 produce significant change in SPR signals in 30 min. Calixarenes layers are used as platforms for molecular recognition, where complementary binding sites are easily and selectively introduced. The aromatic molecules used in this study are anthracene, pyrene, coronene and rubrene. The host-guest properties of these aromatic molecules and the calixarene cavity exhibit selectivity of these aromatic molecules. The anthracene, pyrene and coronene have moderate binding affinity to the cavity, and the rubrene does not bind at all.

15

Levourch, Gaëlle, Noureddine Lebaz e Abdelhamid Elaissari. "Hydrophilic Submicron Nanogel Particles for Specific Recombinant Proteins Extraction and Purification". Polymers 12, n. 6 (24 giugno 2020): 1413. http://dx.doi.org/10.3390/polym12061413.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

In biomedical diagnosis and bionanotechnologies, the extraction and purification of proteins and protein derivatives are of great interest. In fact, to purify recombinant proteins for instance, new methodologies and well appropriate material supports need to be established and also to be evaluated. In this work, hydrophilic nanohydrogel particles were prepared for recombinant proteins extraction for purification purpose. The prepared nanohydrogel polymer-based particles are hydrophilic below the volume phase transition temperature (TVPT) and dehydrated above the TVPT, due to the thermally sensitive poly(N-alkyl acrylamide) and poly(N-alkyl methacrylamide) derivatives. Then, the use of heavy metal ions in the presence of such functional particles should specifically capture recombinant proteins (i.e., proteins bearing a poly(histidine) part). In order to understand and to optimize the specific capture and the purification of recombinant proteins, various parameters have been investigated as a systematic study. Firstly, the adsorption was investigated as a function of pH and protein concentration. According to high hydration of the prepared nanohydrogel, no marked adsorption was observed. Secondly, the effect of pH was investigated and found to be the driven parameter affecting the metal ions immobilization and the recombinant proteins complexation. As a result, high protein complexation was observed at basic pH compared to non-complexation at acidic pH medium. The immobilized proteins via complexation were released by changing the pH. This decomplexation seems to be effective but depends on fixation conditions and particle surface structure.

16

Ashrafi, Frydon, Tahereh Mahbobi e Ashraf Sadat Ghasemi. "Computational study adsorption of mercaptopurine in generation G3 and G5 PAMAM dendrimers". Ciência e Natura 37 (21 dicembre 2015): 12. http://dx.doi.org/10.5902/2179460x20822.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Due to its unique properties of dendrimers as well as with high-level groups, a special ability to carry drugs. In this study compared the interaction between the two generations of poly (amidoamine) PAMAM (G3and G5) dendrimers and the drug 6-mercaptopurine (6-MP) and the drug entrapment within the structure of dendrimers the electrostatic and covalent complexation of drugs to the dendrimer surface have been studied. The use of drug-dendrimer complex enhanced drug solubility and bioavailability of the drug.

17

Grama, Lavinia, Daniela-Lucia Muntean e A. Curticăpean. "Unsaturated Heteropolyoxotungstates with Platinum Cation Complexation". Acta Medica Marisiensis 60, n. 2 (1 aprile 2014): 34–36. http://dx.doi.org/10.2478/amma-2014-0007.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Abstract Background: Polyanions are a special category of coordination compounds with a large development in last years. By coordination of metal oxoions at the lacunary polyoxometalates are obtained new compounds which are studied for theirs possible antitumoral and antiviral activities. The polyoxometalates can bind cations by oxygen atoms from their saturated surface structure or by embedding in vacant sites. Material and method: The methods used for determining cation coordination with the unsaturated polyoxotungstate are spectrophotometry and conductometry. The solutions used in this study were: for ligand a solution of K27[KAsW40O140] and for cation a solution of K2[PtCl6]. The variation of electrical conductivity of ionic species found in solution, caused by their concentrations, decreases during the complex formation, which was determined by conductometry. The spectrophotometric assay was performed to verify ratios between cation:ligand combination, determined by conductometry. Results: The graphical representations of conductivity function of number of moles of added titrant solutions emphasize that there are two types of coordination compounds with two different combination ratios ligand:cation at 1:2 or 1:4. The spectrophotometric determination performed, confirmed these ratios. Conclusions: There are two types of coordination complexes, and the ligand:cation ratios are well known for encrypting polyoxotungstates type used in the study. Besides the main active position SC where K+ alkaline cation is coordinated, it has four active stand side S1-4, which can coordinate metal cations, depending on the size of their cationic radius and the electronic charge they hold.

18

DAI, WEI, RUI LI, HAIQIN JIN e SHIFANG WANG. "MOLECULAR SIMULATION OF HYDROGEN ADSORPTION IN ALUMINUM ORGANIC FRAMEWORK". Modern Physics Letters B 27, n. 13 (10 maggio 2013): 1350095. http://dx.doi.org/10.1142/s0217984913500954.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

With the aid of molecular simulations, a new aluminum organic framework structure is designed, and the hydrogen storage capability of the designed structure is studied using grand canonical Monte Carlo technique. Results show that the hydrogen storage capacity of aluminum organic framework at 77 K and 1 MPa is about 430 hydrogen molecules per unit cell, the corresponding weight density be equivalent to 17.45 wt.%. The preferential adsorption site is located at the aluminum–oxygen cluster. Hydrogen molecules are preferentially distributed on the surface of Al ions. The complexation of organic linkers with Al ions is found to be in favor of the adsorption of hydrogen.

19

Zuo, Youming, Zirui He, Weidong Yang, Chongde Sun, Xingqian Ye, Jinhu Tian e Xiangli Kong. "Preparation of Neohesperidin–Taro Starch Complex as a Novel Approach to Modulate the Physicochemical Properties, Structure and In Vitro Digestibility". Molecules 28, n. 9 (5 maggio 2023): 3901. http://dx.doi.org/10.3390/molecules28093901.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Neohesperidin (NH), a natural flavonoid, exerts multiple actions, such as antioxidant, antiviral, antiallergic, vasoprotective, anticarcinogenic and anti-inflammatory effects, as well as inhibition of tumor progression. In this study, the NH–taro starch complex is prepared, and the effects of NH complexation on the physicochemical properties, structure and in vitro digestibility of taro starch (TS) are investigated. Results showed that NH complexation significantly affected starch gelatinization temperatures and reduced its enthalpy value (ΔH). The addition of NH increased the viscosity and thickening of taro starch, facilitating shearing and thinning. NH binds to TS via hydrogen bonds and promotes the formation of certain crystalline regions in taro starch. SEM images revealed that the surface of NH–TS complexes became looser with the increasing addition of NH. The digestibility results demonstrated that the increase in NH (from 0.1% to 1.1%, weight based on starch) could raise RS (resistant starch) from 21.66% to 27.75% and reduce RDS (rapidly digestible starch) from 33.51% to 26.76% in taro starch. Our work provided a theoretical reference for the NH–taro starch complex’s modification of physicochemical properties and in vitro digestibility with potential in food and non-food applications.

20

Bharadwaj, Namita, e Jaishri Kaushik. "Nano Synthesis and Characterization of Complex Derived from Silver Metal Conjugated with Midodrine Hydrochloride". Oriental Journal Of Chemistry 37, n. 1 (28 febbraio 2021): 157–61. http://dx.doi.org/10.13005/ojc/370121.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

The stability constant Kf for the complexation of Ag(Ⅰ) metal ion with Midodrine hydrochloride were determinedby spectrophotometric method at room temperature .The colored complexes were measured at 300 nm. The stability constant of the complexes were found to be 5.47 by mole ratio method. The stoichiometry of the complexes formed between the Midodrine drug and Ag (Ⅰ) metal ion are 1:1 M/L ratio. Silver conjugated Midodrine hydrochloride Nano synthesized and characterized by UV/Visible spectroscopy, SEM, XRD and FT-IR. The UV/Visible spectra of Midodrine –Ag nanoparticle in the range of 322 nm. XRD conformThe crystallite size of Midodrine - Ag (Ⅰ) nanoparticles are found to be 64.5 nmfrom Debye Scherer formula.Thecrystallinity of nanoparticles is Face centered cubic structure. SEM conform of particle size and surface morphology, FTIR analyzed involvement of -NH2 group in Midodrine is the stabilized of silver nanoparticle. This research is focuses on complexation, Nano synthesis and characterization of Drug-silver nanoparticle for antihypotention therapy.

21

Sharma, Rakesh K. "Design, synthesis, and application of chelating polymers for separation and determination of trace and toxic metal ions. A green analytical method". Pure and Applied Chemistry 73, n. 1 (1 gennaio 2001): 181–86. http://dx.doi.org/10.1351/pac200173010181.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

A green analytical method was developed for separation and preconcentration of trace amounts of copper from aqueous samples using aurin tricarboxylic acid-immobilized silica gel (ATA-SG). This was done by determining chemical speciation and stability constant of Cu-ATA complex. The pH-metric studies indicate strong complexation of Cu with ATA (log bCu2ATA = 19.56). Species distribution curve for Cu-ATA complex indicates almost 100% complexation of copper, with ATA forming Cu2ATA as the predominant species. Considering the selectivity and strong interaction of ATA toward copper, ATA was immobilized on the polymeric matrix of silica gel, and the conditions were optimized for the uptake of copper from the aqueous solutions. The uptake of Cu ions by ATA-SG was studied both by batch and column methods. The method was developed for the estimation of trace amounts of copper in various samples. Molecular modeling studies were also performed on ATA-immobilized silica gel for gaining an insight into the active structure of ATA on the silica surface.

22

Rakhmonova, Dilnoza, Lobar Gapurova, Surayyo Razzoqova, Shakhnoza Kadirova, Batirbay Torambetov, Zukhra Kadirova e Svitlana Shishkina. "5-Amino-1H-benzimidazole-2(3H)-thione: molecular, crystal structure and Hirshfeld surface analysis". Acta Crystallographica Section E Crystallographic Communications 78, n. 2 (28 gennaio 2022): 231–34. http://dx.doi.org/10.1107/s2056989022000792.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

The title compound, C7H7N3S, which has potential biological activity, can be used as a ligand in metal complexation. This compound exists as the thione tautomer in the crystal phase, which is confirmed by the study of its molecular structure. The amino group has pyramidal configuration. In the crystal phase, the two independent molecules in the asymmetric unit form tetramers as a result of N—H...S hydrogen bonds. These tetramers are linked by N—H...N hydrogen bonds, forming chains/tubes in the [010] direction. The Hirshfeld surface analysis showed that the highest contribution to the total surface is provided by H...H interactions as well as S...H/H...S and C...H/H...C contacts associated with X—H...S hydrogen bonds and X—H...C(π) interactions.

23

Wang, Ning, Huihui Du, Qiaoyun Huang, Peng Cai, Xingmin Rong, Xionghan Feng e Wenli Chen. "Surface complexation modeling of Cd(II) sorption to montmorillonite, bacteria, and their composite". Biogeosciences 13, n. 19 (6 ottobre 2016): 5557–66. http://dx.doi.org/10.5194/bg-13-5557-2016.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Abstract. Surface complexation modeling (SCM) has emerged as a powerful tool for simulating heavy metal adsorption processes on the surface of soil solid components under different geochemical conditions. The component additivity (CA) approach is one of the strategies that have been widely used in multicomponent systems. In this study, potentiometric titration, isothermal adsorption, zeta potential measurement, and extended X-ray absorption fine-structure (EXAFS) spectra analysis were conducted to investigate Cd adsorption on 2 : 1 clay mineral montmorillonite, on Gram-positive bacteria Bacillus subtilis, and their mineral–organic composite. We developed constant capacitance models of Cd adsorption on montmorillonite, bacterial cells, and mineral–organic composite. The adsorption behavior of Cd on the surface of the composite was well explained by CA-SCM. Some deviations were observed from the model simulations at pH < 5, where the values predicted by the model were lower than the experimental results. The Cd complexes of X2Cd, SOCd+, R-COOCd+, and R-POCd+ were the predominant species on the composite surface over the pH range of 3 to 8. The distribution ratio of the adsorbed Cd between montmorillonite and bacterial fractions in the composite as predicted by CA-SCM closely coincided with the estimated value of EXAFS at pH 6. The model could be useful for the prediction of heavy metal distribution at the interface of multicomponents and their risk evaluation in soils and associated environments.

24

Topuz, Fuat, e Tamer Uyar. "Electrospinning of Cyclodextrin Functional Nanofibers for Drug Delivery Applications". Pharmaceutics 11, n. 1 (24 dicembre 2018): 6. http://dx.doi.org/10.3390/pharmaceutics11010006.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Electrospun nanofibers have sparked tremendous attention in drug delivery since they can offer high specific surface area, tailored release of drugs, controlled surface chemistry for preferred protein adsorption, and tunable porosity. Several functional motifs were incorporated into electrospun nanofibers to greatly expand their drug loading capacity or to provide the sustained release of the embedded drug molecules. In this regard, cyclodextrins (CyD) are considered as ideal drug carrier molecules as they are natural, edible, and biocompatible compounds with a truncated cone-shape with a relatively hydrophobic cavity interior for complexation with hydrophobic drugs and a hydrophilic exterior to increase the water-solubility of drugs. Further, the formation of CyD-drug inclusion complexes can protect drug molecules from physiological degradation, or elimination and thus increases the stability and bioavailability of drugs, of which the release takes place with time, accompanied by fiber degradation. In this review, we summarize studies related to CyD-functional electrospun nanofibers for drug delivery applications. The review begins with an introductory description of electrospinning; the structure, properties, and toxicology of CyD; and CyD-drug complexation. Thereafter, the release of various drug molecules from CyD-functional electrospun nanofibers is provided in subsequent sections. The review concludes with a summary and outlook on material strategies.

25

Simon Justin, A., P. Vickraman e B. Joji Reddy. "Investigation on Carbonsphere@Nickel Cobalt Sulfide Core-shell Nanocomposite for Asymmetric Supercapacitor Application". Energy Harvesting and Systems 6, n. 1-2 (25 settembre 2019): 1–13. http://dx.doi.org/10.1515/ehs-2019-0003.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Abstract The carbon sphere (CS)@nickel cobalt sulfide core-shell nanocomposite at five different mole ratios have been synthesized by a facile low-temperature water-bath method without any thermal treatment. The XRD results on CS, NiCo2S4 and its ternary complexation confirms nanocomposite formation which matches with the cubic structure. The FTIR confirms the complexation of CS and metal-sulfide core-shell. TEM morphology shows CS at NiCo2S4 forming a core-shell which appears as interlinked bunch of grapes. The BET surface analysis observes the high surface area for the core-shell. The XPS studies confirm the elemental presence and valence states of metal composition of the core-shell. Electrochemical studies on the pure NiCo2S4 and CS@NiCo2S4 have shown that CS@NiCo2S4 in 1:1 ratio (scn2) only exhibits higher specific capacitance of 838 F g−1 at 1 A g−1 with capacity retention of 89 % for 5000 cycles than other mole ratios. Using this scn2, asymmetric supercapacitor (ASC) device fabrication has been studied. The electrochemical studies on ASC reveal high energy density of 101 Wh kg−1 with the power density of 6.3 k W kg−1, and having good cycling stability with 92 % of capacitance retention even after 3000 cycles at 20 A g−1.

26

Yin, Zhou, Johannes Lützenkirchen, Nicolas Finck, Noémie Celaries, Kathy Dardenne e Hans Chr Bruun Hansen. "Adsorption of arsenic(V) onto single sheet iron oxide: X-ray absorption fine structure and surface complexation". Journal of Colloid and Interface Science 554 (ottobre 2019): 433–43. http://dx.doi.org/10.1016/j.jcis.2019.07.024.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Verma, Parveen Kumar, e Prasanta Kumar Mohapatra. "Luminescence spectroscopic investigations of europium complexes formed in the kaolinite-humic acid/citric acid systems". Radiochimica Acta 108, n. 11 (26 novembre 2020): 859–71. http://dx.doi.org/10.1515/ract-2019-3148.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

AbstractIn the present study, the nature of Eu(III) complexes (Eu(III) was used as a surrogate for Am(III)) formed in kaolinite–humic acid (HA)/citric acid (CA) system was investigated by luminescence spectroscopy. In addition to the ternary system (kaolinite + Eu + L(CA/HA)), the binary system (Eu-L) was also looked at for a better understanding of the complexes formed at the kaolinite surface. The lifetime and emission spectra of Eu-L complexes on the kaolinite surface differ considerably as compared to the same in the aqueous phase. The Eu-HA aqueous complexation shows differences in the excitation spectra with similar decay lifetimes with increasing aqueous HA concentrations. The ligand-to-metal charger transfer (LMCT) in the Eu-HA excitation spectra suggests the complexation of Eu(III) with HA at pH ∼ 4. Although the mode of Eu(III) binding to the kaolinite surface in the presence of CA/HA was the same i.e. metal-bridged ternary complex formation, the local surroundings around the sorbed Eu(III) differ in the two cases. The loading of HA in the Eu-HA-kaolinite system does not have a large effect on the local structure around the sorbed Eu(III) ion, but enhances the percentage of Eu(III) uptake onto the kaolinite surface. The number of H2O molecules in the primary hydration sphere of sorbed Eu(III) differs in the Eu-HA-kaolinite and Eu-CA-kaolinite systems. In addition, Eu(III) assisted precipitation of HA was also seen using a radiometric method.

28

de Jonge, L. W., P. Moldrup e P. Schjønning. "Soil Infrastructure, Interfaces & Translocation Processes in Inner Space ("Soil-it-is"): towards a road map for the constraints and crossroads of soil architecture and biophysical processes". Hydrology and Earth System Sciences 13, n. 8 (19 agosto 2009): 1485–502. http://dx.doi.org/10.5194/hess-13-1485-2009.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Abstract. Soil functions and their impact on health, economy, and the environment are evident at the macro scale but determined at the micro scale, based on interactions between soil micro-architecture and the transport and transformation processes occurring in the soil infrastructure comprising pore and particle networks and at their interfaces. Soil structure formation and its resilience to disturbance are highly dynamic features affected by management (energy input), moisture (matric potential), and solids composition and complexation (organic matter and clay interactions). In this paper we review and put into perspective preliminary results of the newly started research program "Soil-it-is" on functional soil architecture. To identify and quantify biophysical constraints on soil structure changes and resilience, we claim that new approaches are needed to better interpret processes and parameters measured at the bulk soil scale and their links to the seemingly chaotic soil inner space behavior at the micro scale. As a first step, we revisit the soil matrix (solids phase) and pore system (water and air phases), constituting the complementary and interactive networks of soil infrastructure. For a field-pair with contrasting soil management, we suggest new ways of data analysis on measured soil-gas transport parameters at different moisture conditions to evaluate controls of soil matrix and pore network formation. Results imply that some soils form sponge-like pore networks (mostly healthy soils in terms of agricultural and environmental functions), while other soils form pipe-like structures (agriculturally poorly functioning soils), with the difference related to both complexation of organic matter and degradation of soil structure. The recently presented Dexter et al. (2008) threshold (ratio of clay to organic carbon of 10 kg kg−1) is found to be a promising constraint for a soil's ability to maintain or regenerate functional structure. Next, we show the Dexter et al. (2008) threshold may also apply to hydrological and physical-chemical interface phenomena including soil-water repellency and sorption of volatile organic vapors (gas-water-solids interfaces) as well as polycyclic aromatic hydrocarbons (water-solids interfaces). However, data for differently-managed soils imply that energy input, soil-moisture status, and vegetation (quality of eluded organic matter) may be equally important constraints together with the complexation and degradation of organic carbon in deciding functional soil architecture and interface processes. Finally, we envision a road map to soil inner space where we search for the main controls of particle and pore network changes and structure build-up and resilience at each crossroad of biophysical parameters, where, for example, complexation between organic matter and clay, and moisture-induced changes from hydrophilic to hydrophobic surface conditions can play a role. We hypothesize that each crossroad (e.g. between organic carbon/clay ratio and matric potential) may control how soil self-organization will manifest itself at a given time as affected by gradients in energy and moisture from soil use and climate. The road map may serve as inspiration for renewed and multi-disciplinary focus on functional soil architecture.

29

Xing, Zhaoliang, Chong Zhang, Naifan Xue, Zhihui Li, Fei Li, Xiangnan Wan, Shaowei Guo e Jianhong Hao. "High-Frequency Surface Insulation Strength with Nanoarchitectonics of Disiloxane Modified Polyimide Films". Polymers 14, n. 1 (31 dicembre 2021): 146. http://dx.doi.org/10.3390/polym14010146.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

High-frequency power transformers are conducive to the reliable grid connection of distributed energy sources. Polyimide is often used for the coating insulation of high-frequency power transformers. However, creeping discharge will cause insulation failure, therefore, it is necessary to use disiloxane for the purpose of modifying the molecular structure of polyimide. This paper not only introduces 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (GAPD) with a molar content of 1%, 2%, and 5% to polyimide, but also tests both the physical and chemical properties of the modified film and the high frequency creeping dielectric strength. The results show that after adding GAPD, the overall functional groups of the material do not change, at the same time the transfer complexation of intermolecular charge and the absorption of ultraviolet light increase. There is no phase separation of the material and the structure is more regular and ordered, moreover the crystallinity increases. The overall dielectric constant and the dielectric loss tangent value show different trends, which means that the former value increases, while the latter value decreases. In addition, the resistivity of the surface and the volume increase, which is the same as the glass transition temperature. The mechanical properties are excellent, and the strength of bulk breakdown is mounting. The insulation strength of the high frequency creeping surface has been improved, which will increase with larger contents of GAPD. Among them, the relative change of the creeping flashover voltage is not obvious, and the creeping discharge life of G5 is 4.77 times that of G0. Further analysis shows that the silicon-oxygen chain links of the modified film forms a uniformly dispersed Si-O-Si network in the matrix through chemical bonds and charge transfer complexation. Once the outer matrix is destroyed, it will produce dispersed flocculent inorganic particles which have the role of protecting the inner material and improving the performance of the material. Combined with the ultraviolet light energy absorption, the increase of deep traps, the reduction of dielectric loss, and the improvement of thermodynamic performance, can better improve the high-frequency creeping insulation strength of polyimide film and its potential application value.

30

Lodeiro, Pablo, Adrian Fuentes, Roberto Herrero e Manuel E. Sastre de Vicente. "CrIII binding by surface polymers in natural biomass: the role of carboxylic groups". Environmental Chemistry 5, n. 5 (2008): 355. http://dx.doi.org/10.1071/en08035.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Environmental context. Large quantities of chromium are discharged into the environment as a result of its widespread use in modern industries, and consequently, chromium could constitute a serious pollution problem. Adsorption onto natural biomass offers real potential as a way of removing chromium from the environment, because such adsorbents contain biopolymers with particular chemical stability and selectivity towards metals. In addition, natural biomass constitutes an eco-friendly and cost-effective alternative to the existing methods. Here, specific interactions between chromium and the biomass are investigated. Abstract. The chromium(III)-binding capacity of several biomaterials has been described under fixed conditions of pH (4.5) and initial metal concentration (100 mg L–1). Three of these materials (Sargassum muticum, orange peel and bracken fern) have been selected and subjected to different studies. Fourier transform infrared and scanning electron microscopy techniques were used to describe the structure of the biomaterials, supporting the hypothesis of a mechanism of metal complexation via carboxylic groups. Potentiometric titrations revealed the quantity of carboxyl groups present in S. muticum, orange peel and bracken fern: 1.78, 0.49 and 0.67 mmol g–1, respectively. Moreover, a model considering different types of binding sites was used to simulate the process and determine the apparent pK values of the main functionalities. The number of carboxylic groups was clearly correlated with the maximum amount of CrIII binding by the materials. A Langmuir competitive model was used to determine the complexation constants for chromium, log KCr, which are very close (~3), supporting the idea of the implication of essentially one acid functionality. Desorption studies were conducted for different times employing H2SO4 and sodium citrate.

31

Chroni, Angeliki, Aleksander Forys, Barbara Trzebicka, Adam Alemayehu, Vaclav Tyrpekl e Stergios Pispas. "Poly[oligo(ethylene glycol) methacrylate]-b-poly[(vinyl benzyl trimethylammonium chloride)] Based Multifunctional Hybrid Nanostructures Encapsulating Magnetic Nanoparticles and DNA". Polymers 12, n. 6 (3 giugno 2020): 1283. http://dx.doi.org/10.3390/polym12061283.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

We report on the preparation of novel and multifunctional hybrid spherical-shaped nanostructures involving a double-hydrophilic block copolymer, namely the neutral cationic poly[oligo(ethylene glycol) methacrylate]-b-poly[(vinyl benzyl trimethylammonium chloride)] (POEGMA-b-PVBTMAC) diblock copolymer, initially complexed with hydrophilic anionic magnetic nanoparticles (MNPs), and subsequently, with short deoxyribonucleic acid (113 bases DNA). The POEGMA-b-PVBTMAC copolymer, the copolymer/MNPs and the copolymer/MNPs/DNA tricomponent hybrid electrostatic complexes were studied by dynamic/electrophoretic light scattering (DLS/ELS) and cryogenic transmission electron microscopy (cryo-TEM) techniques for the determination of their structure and solution properties. The MNPs were complexed efficiently with the oppositely charged diblock chains, leading to well-defined hybrid organic–inorganic spherical-shaped nanostructures. A significant aggregation tendency of the MNPs is noticed in cryo-TEM measurements after the electrostatic complexation of DNA, implying an accumulation of the DNA macromolecules on the surface of the hybrid tricomponent complexes. Magnetophoretic experiments verified that the MNPs maintain their magnetic properties after the complexation initially with the copolymer, and subsequently, within the block polyelectrolyte/MNPs/DNA nanostructures.

32

Ding, Jiajia, Yu Tian, Tao Lu e Jiang Kang. "Study on the adsorption of heavy metals by biochar modified with different modifiers under room temperature". E3S Web of Conferences 293 (2021): 03014. http://dx.doi.org/10.1051/e3sconf/202129303014.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

In order to obtain an environment-friendly biochar adsorption material with excellent adsorption performance, the biochar made from corn straw was modified with FeCl3, Na2S and KMnO4 as modifiers, and the adsorption effect of biochar on several heavy metal ions in water before and after modification was studied. The properties of biochar before and after modification were characterized by SEM, XRD, FTIR and BET, and the adsorption mechanism was discussed. The results showed that the three modified reagents could effectively improve the adsorption capacity of biochar for three heavy metal ions in water, and the adsorption effect was still good at room temperature. The adsorption difference is related to the specific surface area, pore structure, aromatic structure and SiO2 content of biochar. The adsorption mechanism mainly includes the complexation reaction between physical adsorption and surface functional groups. This study is beneficial to promote the resource utilization of agricultural and forestry waste biomass, and provides a certain reference basis for related research.

33

Santo, Kolattukudy P., e Alexander V. Neimark. "Effects of metal-polymer complexation on structure and transport properties of metal-substituted polyelectrolyte membranes". Journal of Colloid and Interface Science 602 (novembre 2021): 654–68. http://dx.doi.org/10.1016/j.jcis.2021.06.018.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Abraham, Leggins, Tiju Thomas e Moorthi Pichumani. "Correlation of micellar aggregation – complexation regimes to discern stability of micellar structure and nano-encapsulation". Journal of Colloid and Interface Science 547 (luglio 2019): 234–44. http://dx.doi.org/10.1016/j.jcis.2019.04.003.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Bystrický, Slavomír, Anna Malovíková, Tibor Sticzay e Karel Bláha. "Complexation of poly(Lys-Ala) and poly(Lys-Ala-Ala-Ala) with pectins and potassium oligogalacturonates". Collection of Czechoslovak Chemical Communications 53, n. 11 (1988): 2833–42. http://dx.doi.org/10.1135/cccc19882833.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

The selected model polypeptides poly(Lys-Ala) and poly(Lys-Ala-Ala-Ala) underwent a helix-forming interaction with potassium pectates and pectinates of various esterification degree (E) and with some potassium oligogalacturonates (n = 2-5, 9, 13). Formation of the complex quantitatively monitored by a circular dichroic measurement showed that the specific band distribution of charged side chains of lysine units at the surface of helical structure does not constitute grounds for the local mode of interaction. Potassium pectinate of esterification degree E 57%, corresponding to polypeptides by charge density, does not reveal enhanced complexation values. The complex-forming efficacy continuously decreases with the increase of the esterification degree of pectin. Saturation of charges of the polypeptide was achieved predominantly by the spatial action of the superhelical structure of D-galacturonate chains.

36

Andrews, Mark A., Eric J. Voss, George L. Gould, Wim T. Klooster e Thomas F. Koetzle. "Regioselective Complexation of Unprotected Carbohydrates by Platinum(II): Synthesis, Structure, Complexation Equilibria, and Hydrogen-Bonding in Carbonate-Derived Bis(phosphine)platinum(II) Diolate and Alditolate Complexes". Journal of the American Chemical Society 116, n. 13 (giugno 1994): 5730–40. http://dx.doi.org/10.1021/ja00092a025.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Pokrovsky, O. S., G. S. Pokrovski e J. Schott. "Gallium(III) adsorption on carbonates and oxides: X-ray absorption fine structure spectroscopy study and surface complexation modeling". Journal of Colloid and Interface Science 279, n. 2 (novembre 2004): 314–25. http://dx.doi.org/10.1016/j.jcis.2004.06.095.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Mizuhata, Yoshiyuki, Takahiro Sasamori, Nobuhiro Takeda e Norihiro Tokitoh. "A Stable Neutral Stannaaromatic Compound: Synthesis, Structure and Complexation of a Kinetically Stabilized 2-Stannanaphthalene". Journal of the American Chemical Society 128, n. 4 (febbraio 2006): 1050–51. http://dx.doi.org/10.1021/ja057531d.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Shi, Min-Min, Mang Wang e Hong-Zheng Chen. "Preparation and photoconductivity of PVP-CoPc self-assembled film". Journal of Materials Research 13, n. 12 (dicembre 1998): 3550–54. http://dx.doi.org/10.1557/jmr.1998.0483.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Through the complexation of cobalt phthalocyanine (CoPc) and a film of poly[4-vinyl- pyridine] (PVP) polarized by an electric field, a new type of preferentially oriented self-assembled film (PVP-CoPc) was obtained. The characterization of the film by differential scanning calorimetry (DSC), angle-dependent x-ray photoelectron spectroscopy (XPS), and Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS) revealed that the planes of pyridine rings oriented perpendicular to the film surface, while the planes of phthalocyanine rings were oriented parallel with, and coordinated on, the film surface. Photoconductivity study showed that the photoconductivities of the photoreceptors (PR's) made from the PVP-CoPc self-assembled film were much better than those from CoPc alone. These changes were ascribed to the charge transfer and the unique and ordered structure of PVP-CoPc self-assembled film.

40

Dan, Y., S. Y. Chen e T. J. Lian. "Surface structure and properties of water-based polymer coating materials prepared by the complexation of two polymer latices with chemically complementary structures". Journal of Applied Polymer Science 90, n. 7 (22 settembre 2003): 1748–54. http://dx.doi.org/10.1002/app.12664.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Huang, Xing Qi, Xiao Rong Li, Da Wei Zhang, Chang Jun Xue e Ai Qin Zhang. "Application of Polycarboxylate Superplasticizer in the Concrete". Materials Science Forum 898 (giugno 2017): 2076–80. http://dx.doi.org/10.4028/www.scientific.net/msf.898.2076.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Compared with the traditional water reducer, polycarboxylicwater-reducing agent exhibits the advantages of high water-reducing rate, cement paste fluidity and low slump loss, etc. The structure of polycarboxylates water reducing agent molecular is comb type. Water reducing agent can be used in the molecular design because it has high water reducing rate, low dosage, good slump stability, and have great potential in increase strength. In recent years, it has attracted many researchers' attention. Water reducing agent can block or destroy cement granular flocculation structure, through the surface function, complexation, electrostatic repulsion force and stereo repulsive force. Research on water reducing agent based on the application of poly carboxylic acid can realize functional design of water reducing agent, so as to promote the development of high-performance concrete.

42

Abdala, Dalton Belchior, Paul Andrew Northrup, Yuji Arai e Donald Lewis Sparks. "Surface loading effects on orthophosphate surface complexation at the goethite/water interface as examined by extended X-ray Absorption Fine Structure (EXAFS) spectroscopy". Journal of Colloid and Interface Science 437 (gennaio 2015): 297–303. http://dx.doi.org/10.1016/j.jcis.2014.09.057.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Burdonov, A. E., N. V. Vchislo, E. A. Verochkina e I. B. Rozentsveig. "Synthesis of new dithiocarbamate and xanthate complexes and their application in enrichment processes". Proceedings of Universities. Applied Chemistry and Biotechnology 13, n. 2 (1 luglio 2023): 160–71. http://dx.doi.org/10.21285/2227-2925-2023-13-2-160-171.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Ore flotation is the main and defining technological process in ore benefication and non-ferrous metals production. The flotation process requires the use of a variety of chemical reagents, including collectors, frothers, surface modifiers, and pH regulators. The development and selection of suitable reagents for the processed material play a vital role in efficient flotation. The flotation activity of collectors depends fundamentally on the composition and structure of the hydrophobic and hydrophilic fragments forming the flotation agent molecule, as well as on the nature of the ore that undergoes flotation processing. In this regard, the identification and study of the “substance structure–flotation activity” relation, as well as the search for new effective flotation reagents gain importance within applied organic and organoelement chemistry and related branches of science and technology. In this article, we review syntheses of effective collector reagents, namely xanthates and dithiocarbamates, based on the literature data for the past five years. Where necessary, earlier sources are provided. The reaction conditions and yields of the target compounds are presented using schemes. In addition, we present the results of flotation tests on the surfaces of various ores and the data on the mechanism of concentrate extraction. According to the reviewed publications, the fixation of collector reagents on the surface of minerals can be regarded as a complexation process of the collector functional groups and metal ions located on the surface of the mineral.

44

Karwan, Omer Ali, Ali Mohamad Hikmat, Thomas Gerber e Eric Hosten. "Zinc(II) Complex Containing Oxazole Ring: Synthesis, Crystal Structure, Characterization, DFT Calculations, and Hirshfeld Surface Analysis". Acta Chimica Slovenica 69, n. 4 (15 dicembre 2022): 906–12. http://dx.doi.org/10.17344/acsi.2022.7682.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

A new complex of Zn(II), with 5-chloro-2-methylbenzoxazole ligand (L), has been synthesized by the reaction of zinc dichloride with the ligand (L= C8H6ClNO) in ethanol solution: dichloridobis(5-chloro-2-methyl-1,3-benzoxazole)-zinc(II), C16H12Cl4N2O2Zn. The synthesized complex has been fully characterized by elemental analysis, molar conductivity, FT‑IR, UV‑Vis, and single-crystal X-ray diffraction (XRD). The XRD analysis reveals that the complex has a 1:2 metal-to-ligand ratio. The zinc(II) complex has a distorted tetrahedral geometry with two coordinated nitrogen atoms from the ligand. Density Functional Theory (DFT) calculations were performed at the B3LYP level of theory using the LANL2DZ basis set for metal complex and the 6–31G(d) basis set for non-metal elements to determine the optimum geometry structure of the complex, and the calculated HOMO and LUMO orbital energies were presented. A natural bond orbital (NBO) analysis was carried out on the molecules to analyze the atomic charge distribution before and after the complexation of the ligand. The Hirshfeld surface mapped over dnorm, shape index, and curvature exhibited strong H... Cl/Cl...H and H...H intermolecular interactions as the principal contributors to crystal packing.

45

Pantaleone, Stefano, Cecilia Irene Gho, Riccardo Ferrero, Valentina Brunella e Marta Corno. "Exploration of the Conformational Scenario for α-, β-, and γ-Cyclodextrins in Dry and Wet Conditions, from Monomers to Crystal Structures: A Quantum-Mechanical Study". International Journal of Molecular Sciences 24, n. 23 (27 novembre 2023): 16826. http://dx.doi.org/10.3390/ijms242316826.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Cyclodextrins (CDs) constitute a class of cyclic oligosaccharides that are well recognized and largely applied in the drug delivery field, thanks to their biocompatibility, low cost, and the possibility to be derivatized in order to tune and optimize the complexation/release of the specific drug. The conformational flexibility of these systems is one of their key properties and requires a cost-effective methodology to be studied by combining the accuracy of results with the possibility of exploring a large set of conformations. In the present paper, we have explored the conformational potential energy surface of the monomers and dimers of α-, β-, and γ-cyclodextrins (i.e., 6, 7, and 8 monomeric units, respectively) by means of fast but accurate semiempirical methods, which are then refined by state-of-the-art DFT functionals. Moreover, the crystal structure is considered for a more suitable comparison with the IR spectrum experimentally recorded. Calculations are carried out in the gas phase and in water environments, applying both implicit and explicit treatments. We show that the conformation of the studied molecules changes from the gas phase to the water, even if treated implicitly, thus modifying their complexation capability.

46

Sorokina, Svetlana A., e Zinaida B. Shifrina. "Dendrimers as Antiamyloid Agents". Pharmaceutics 14, n. 4 (31 marzo 2022): 760. http://dx.doi.org/10.3390/pharmaceutics14040760.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Dendrimer–protein conjugates have significant prospects for biological applications. The complexation changes the biophysical behavior of both proteins and dendrimers. The dendrimers could influence the secondary structure of proteins, zeta-potential, distribution of charged regions on the surface, the protein–protein interactions, etc. These changes offer significant possibilities for the application of these features in nanotheranostics and biomedicine. Based on the dendrimer–protein interactions, several therapeutic applications of dendrimers have emerged. Thus, the formation of stable complexes retains the disordered proteins on the aggregation, which is especially important in neurodegenerative diseases. To clarify the origin of these properties and assess the efficiency of action, the mechanism of protein–dendrimer interaction and the nature and driving force of binding are considered in this review. The review outlines the antiamyloid activity of dendrimers and discusses the effect of dendrimer structures and external factors on their antiamyloid properties.

47

Yi, Man, e Yucheng Chen. "Enhanced phosphate adsorption on Ca-Mg-loaded biochar derived from tobacco stems". Water Science and Technology 78, n. 11 (28 dicembre 2018): 2427–36. http://dx.doi.org/10.2166/wst.2019.001.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Abstract Tobacco stems were used as precursors to prepare biochars (YGs) and develop Ca-Mg-loaded biochars (CMYGs) to enhance phosphate adsorption from aqueous solutions. Some influencing factors, such as pH, adsorption time, temperature, and structure characterization, were investigated. Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns showed several new peaks, indicating that Mg(OH)2 and MgO have been present on the surface of the CMYGs. The adsorption could reach equilibrium in 100 min reaction. The equilibrium data were well described by the Langmuir and Freundlich model. After five recycles, the phosphate removal capacity of CMYGs biochar retained over 50%. Moreover, the XRD and FTIR analyses showed that the phosphate sorption mechanisms involved surface electrostatic attraction, inner-sphere complexation and precipitation reactions. Overall, the soaking method could be used to effectively load Mg2+ onto the surface of YGs. The CMYGs synthesized at 750 °C is a promising adsorbent for phosphate removal with a high adsorption capacity for phosphate-polluted wastewater.

48

Karlsson, Björn C. G., John O’Mahony, Jesper G. Karlsson, Helen Bengtsson, Leif A. Eriksson e Ian A. Nicholls. "Structure and Dynamics of Monomer−Template Complexation: An Explanation for Molecularly Imprinted Polymer Recognition Site Heterogeneity". Journal of the American Chemical Society 131, n. 37 (23 settembre 2009): 13297–304. http://dx.doi.org/10.1021/ja902087t.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

49

Gornukhina, Olga V., Irina A. Vershinina, Alexey N. Kiselev, Elizaveta M. Kuvshinova, Sergey A. Syrbu e Oleg A. Golubchikov. "5-[4'-(1, 3-BENZOTHIAZOL-2-YL)PHENYL]-2,3,7,8,12,18-HEXAMETHYL-13,17-DI-N-AMYLPORPHIRIN: SYNTHESIS, COORDINATION PROPERTIES AND SORPTION ON POLYPROPYLENE MATERIALS". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 61, n. 1 (21 dicembre 2017): 49. http://dx.doi.org/10.6060/tcct.20186101.5715.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

5-[4'-(1,3-Benzothiazol-2-yl)phenyl]-2,3,7,8,12,18-hexamethyl-13,17-di-n-amyl-porphirin was synthesized and its coordination properties with the acetates of cobalt, copper and zinc in acetic acid and pyridine were investigated. On the base of data obtained the kinetic parameters of the complexation reaction were calculated. It was established that in acetic acid the increase in a rate of reaction of complexation is observed in the series: Co+2 < Zn+2 < Cu+2, while the activation energy decreases by a factor of 1.5-2 and the value of preexponential factor is significantly increased. The pyridine is an inverse relationship. Copper and cobalt complexes of porphyrin were used for surface modification of chemically activated polypropylene materials. Based on the electronic spectra, the effective surface concentration of immobilized porphyrin molecules was calculated. It was shown, that there is a direct dependence of the amount of grafted metal complexes on the surface structure of the polymer-carrier and conditions of immobilization of macromolecules. The obtained modified materials were tested for bioactivity with the use of an aqueous suspension of agar-agar infected on the following cultures: Staphylococcus aureus (gram-positive culture) and Escherichia coli (gram-negative culture) in the microbial load of 106 cells/ml. The results of the studies were showed that the obtained materials have bacteriostatic resistance to all types of used pathogens.Forcitation:GornukhinaO.V., VershininaI.A., KiselevA.N., KuvshinovaE.M., SyrbuS.A., GolubchikovO.A. 5-[4'-(1, 3-Benzothiazol-2-yl)phenyl]-2,3,7,8,12,18-hexamethyl-13,17-di-n-amylporphirin: synthesis, coordinationpropertiesandsorptiononpolypropylenematerials. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 49-54

50

Li, Wenqi, Liping Zhang, Ying Guan, Zhihan Tong, Xiang Chen, Guanqiao He e Hui Gao. "A slow pyrolysis biochar derived from Tetrapanax papyriferum petiole as an effective sorbent for removing copper ions from aqueous solution". BioResources 14, n. 2 (18 aprile 2019): 4430–53. http://dx.doi.org/10.15376/biores.14.2.4430-4453.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Biochar derived from Tetrapanax papyriferum petioles at different pyrolysis temperatures was used to remove copper from aqueous solution. Abundant porous structures were observed with scanning electron microscopy, and transmission electron microscope images revealed a unique layered nanopore structure. A high pyrolytic temperature resulted in a biochar with a higher surface area, ash content, and mineral element content. The maximum adsorption capacity of T. papyriferum petiole biochar (TBC) was 182 mg/g. The Langmuir adsorption isotherm model and pseudo-second-order kinetics model were most suitable for describing the adsorption process, indicating that adsorption takes place at specific homogeneous sites within the adsorbent. The calculated ΔH° values indicated that the adsorption process was endothermic. The adsorption mechanism for TBC was attributed to precipitation, ion exchange, C-π interactions, and complexation. Thus, the biochar used in this study is a promising environmentally friendly and effective adsorbent for removing Cu2+ ions from an aqueous solution.

Articoli di riviste sul tema "Surface complexation structure"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili