An ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique combined with a sol-gel process for selective solid-phase extraction of cadmium(II)

A new ion-imprinted thiol-functionalized silica gel sorbent was synthesized by a surface imprinting technique in combination with a sol-gel process for selective on-line, solid-phase extraction of Cd(II). The Cd(II)-imprinted thiol-functionalized silica sorbent was characterized by FT-IR, the static adsorption-desorption experiment, and the dynamic adsorption-desorption method. The maximum static adsorption capacity of the ion-imprinted functionalized sorbent was 284 micromol g(-1). The largest selectivity coefficient for Cd(II) in the presence of Pb(II) was over 220. The static uptake capacity and selectivity coefficient of the ion-imprinted functionalized sorbent are higher than those of the nonimprinted sorbent. The breakthrough capacity and dynamic capacity of the imprinted functionalized silica gel sorbent for 4 mg L(-1) of Cd(II) at 5.2 mL min(-1) of sample flow rate were 11.7 and 64.3 micromol g(-1), respectively. No remarkable effect of sample flow rate on the dynamic capacity was observed as the sample flow rate increased from 1.7 to 6.8 mL min(-1). The imprinted functionalized silica gel sorbent offered a fast kinetics for the adsorption and desorption of Cd(II). The prepared ion-imprinted functionalized sorbent was shown to be promising for on-line, solid-phase extraction coupled with flame atomic absorption spectrometry for the determination of trace cadmium in environmental and biological samples. All competitive ions studied did not interfere with the determination of Cd(II). With a sample loading flow rate of 8.8 mL min(-1) for 45-s preconcentration, an enhancement factor of 56, and a detection limit (3sigma) of 0.07 microg L(-1) were achieved at a sampling frequency of 55 h(-1). The precision (RSD) for 11 replicate on-line sorbent extractions of 8 mug L(-1) Cd(II) was 0.9%. The sorbent also offered good linearity (r = 0.9997) for on-line, solid-phase extraction of trace Cd(II).     

Borosilicate glasses modified with organic ligands: a new selective approach for the removal of uranyl ion

Barium borosilicate glass was found to have high uptake capacity for many cations. To improve its selectivity, surface modification was carried out. In order to make the glass selective towards uranyl ion, organic ligands like tri-n-octylphosphine oxide (TOPO) and 8-hydroxy quinoline (Oxine) were used. It was observed that the surface modification resulted in the change in uptake property of the glass. The uptake process was faster and within 5 h, 90% of the uranyl ion could be taken up from a 0.01 mM solution. With use of the modified barium borosilicate glass and EDTA as masking agent, uranyl ion could be selectively removed from mixtures of cations.     

A mesoporous silica functionalized by a covalently bound pyridine derivative for selective optical sensing of thymidine

Fluorescent receptor 1 immobilized mesoporous silica (FMS) possessing the diaminopyridine moiety as a fluorescent receptor was fabricated by sol-gel reaction. The binding ability of FMS with nuclobases was evaluated by fluorophotometry. Interestingly, among nucleobases, addition of thymidine to a suspension of FMS in water resulted in the largest decrease in fluorescence intensity of diaminopyridine in FMS. These results indicate that FMS recognizes selectively thymidine in nucleobase.     

Aluminium oxide grafted on silica gel surface: Study of the thermal stability, structure and surface acidity

The synthesis of aluminium oxide grafted on silica gel surface was carried out by the reaction of a suitable aluminium precursor with the surface hydroxyl groups, SiOH, of the oxide support in non-aqueous solvent. The advantage of this preparation method, compared to the conventional ones (impregnation or precipitation and calcination), is that the oxide is highly dispersed on the surface (monolayer or submonolayer). The resulting material, SiO₂/Al₂O₃, was heat treated at temperature range of 423 to 1573 K. The Al/Si atomic ratios, determined by X-ray photoelectron spectroscopy (XPS), showed that aluminium is less mobile up to heat treatment of 1173 K and above this temperature part of it diffuses to the interior of the matrix. ²⁷Al solid state nuclear magnetic resonance spectroscopy (NMR) showed two different environments, tetrahedral and octahedral for sample calcined up to 1023 K and above this temperature, aluminium in a trigonal bipyramidal environment was also detected. Pyridine adsorbed on a Lewis acid sites were observed for samples calcined up to 1023 K, and above this temperature they were not detected.     

One-step synthesis of unique silica particles for the fabrication of bionic and stably superhydrophobic coatings on wood surface

The silica particles with unique morphology and hydrophobicity have been synthesized via a drop-coating method. After this one-step sol–gel process, silica particles as well as polystyrene were employed in the bionic and stably superhydrophobic coatings on wood surface (with water contact angle of 153 ± 1° and sliding angle less than 5 ± 0.5°). Scanning electron microscopic (SEM) studies revealed that the composite coatings possess two dimensional hierarchical structures comprising of micron scale papilla and submicron scale granules. The synergistic effect of micron/submicron binary structure and low surface energy layer was responsible for the superhydrophobicity of wood surface. Moreover, the chemical and mechanical stabilities of treated wood have been investigated as well, and the results show that the product possesses superhydrophobic property in a wide extent, such as pure water, corrosive water under both acidic and basic conditions, and some common organic solvents. More importantly, it will offer an opportunity to extend the range of practical applications for wood resources.     

表面印迹聚烯丙基胺硅胶材料的制备研究

以硅胶为基体,聚烯丙基胺(PAA)为表面修饰剂,ECH为交联剂,制备了铜表面印迹材料IIP-PAA/SiO2。考察了印迹条件对印迹材料吸附性能的影响,结果为:n(Cu2+):n(N)为0.5,n(ECH):n(N)为0.6,印迹温度323K,时间3h,甲醇为反应介质。合成的IIP-PAA/SiO2材料对Cu(Ⅱ)的吸附性能明显优于PAA/SiO2和NIP材料。在相同条件下,印迹材料的铜吸附量达到0.631mmol·g-1,铜锌选择性系数为56.3,相对选择性系数为26.0。另外印迹材料具有再生吸附性能,经过5次吸附-解吸循环后,其吸附容量维持在90.2%以上。     

Study on the biostability of chlorophyll a entrapped in silica gel nanomatrix

Chlorophyll a has been extracted mainly from fresh leaves and subsequently entrapped in nano porous silica gel matrix through the sol gel route under varying pH conditions. UV–VIS spectroscopy fluorescence and FTIR spectroscopy have been carried out to study the structure and stability of entrapped chlorophyll as a function of sol pH and time after entrapment. It is observed that chlorophyll molecules remain structurally unaltered on entrapment of sol pH of 6.8. Increasing acidic condition indicates gradual changes of chlorophyll extracts e.g., removal of Mg. However once entrapped chlorophyll molecules remain stable irrespective of the sol pH condition. Chlorophyll molecules entrapped in silica gel matrix also appear resistant to degradation by water. It has been proposed that pyroll type ring of the porphyrene moiety forms a weak bond with the unfilled d orbital of the matrix silicon. This imparts stabilization of chlorophyll within silica gel matrix, without any external stabilization agent.     

Effects of the concentrations of precursor and catalyst on the formation of monodisperse silica particles in sol–gel reaction

The monodispersed hybrid silica particles could be synthesized through the one-step sol–gel reaction with organosilane (3-mercaptopropyl trimethoxysilane, MPTMS) in aqueous solution. In this study, the effects of the concentrations of organosilane and the catalyst ((NH₄OH) on the formation of silica particles were investigated. For the first time we reported the successful one-step synthesis of monodisperse hybrid silica particles using organosilane chemicals in the previous study. In order to obtain better insight about the reaction processes, the silica particles were prepared in the presence of various concentrations of MPTMS and NH₄OH. On the basis of the experimental results, it was found that particle size increases as the concentration of organosilane increases. Also, as the concentration of catalyst increases, the diameter of these monodisperse particles decreases significantly. This research can contribute to a new broad avenue for the surface functionalization and hybrid material formation with various sizes.     

Preparation of imprinted polymers at surface of magnetic nanoparticles for the selective extraction of tadalafil from medicines

In this paper, highly selective core-shell molecularly imprinted polymers (MIPs) of tadalafil on the surface of magnetic nanoparticles (MNPs) were prepared. Three widely used functional monomers 2-(trifluoromethyl) acrylic acid (TFMAA), acrylic acid (AA), and methacrylic acid (MAA) were compared theoretically as the candidates for MIP preparation. MIP-coated magnetic nanoparticles (MIP-coated MNPs) showed large adsorption capacity, high recognition ability, and fast binding kinetics for tadalafil. Furthermore, because of the good magnetic properties, MIP-coated MNPs can achieve rapid and efficient separation with an external magnetic field simply. The resulting MIP-coated MNPs were used as dispersive solid-phase extraction (DSPE) materials coupled with HPLC-UV for the selective extraction and detection of tadalafil from medicines (herbal sexual health products). Encouraging results were obtained. The amounts of tadalafil that were detected from the herbal sexual health product was 43.46 nmol g(-1), and the recoveries were in the range of 87.36-90.93% with the RSD < 6.55%.     

Preparation of xylenol orange functionalized silica gel as a selective solid phase extractor and its application for preconcentration--separation of mercury from waters

A new selective solid phase extractor was prepared from silica gel modified with xylenol orange (SGMXO). The solid phase extractor is stable in 6molL(-1) HCl, common organic solvents, and pH 1.0-9.0 buffer solutions. In the batch experiments, Hg(II) can be adsorbed on SGMXO at pH 1.0 with 90.0% retention, whereas the retention of other common coexisting metal ions such as Cd(II), Pb(II), Cu(II), Ni(II), Co(II), Mn(II), Zn(II), and Fe(III) is less than 4.1%.. The adsorption equilibration for Hg(II) was achieved within 3min. At optimum conditions, the adsorption capacity of the extractor is 18.26micromolg(-1) of dry modified silica gel, and the preconcentration factor is as high as 333. The recovery is still higher than 95% for the preconcentration of 10ngmL(-1) Hg(II). The new solid phase extractor has been used for the preconcentration of low level of Hg(II) in surface water, tap water in chemistry laboratory and student's dormitory and a simulated sea water samples, recoveries of 98.2-100.6% were obtained. It is showed that low level of Hg(II) can be effectively preconcentrated by this new selective solid phase extractor.     

A simple method for the quantification of molecular decorations on silica particles

A simple, rapid quantitative approach to determining attachment density on silica nanoparticles has been demonstrated using attenuated total reflectance Fourier transform infrared spectroscopy and verified by thermogravimetric analysis. A very high attachment of approximately 5 attachments per nm² has been achieved through photoinduced thiol–ene click reaction of 11-bromo-1-undecene with a thiol functionalized silica nanoparticle formed from mercaptopropyltrimethoxysilane as the sole precursor. Attachment density with concentration of alkene and reaction time is shown to be highly nonlinear and appears to be limited by accessability of thiols on the surface of the particle. This method opens the opportunity to form nanoparticles with controlled functionality including multifunctional particles, which have been produced in this work.     

EFfect of the parameters of methylens chlorids carbonization on silica gel surface on the properties of an adsorbent (carbosil)

The properties of carbon-silica adsorbents (carbosils) prepared under dynamic conditions, using special apparatus, were investigated. On the surface of silica gel of Merck Si 100, methylene chloride was thermally decomposed. The influence of such factors as pyrolysis temperature, amount of CH₂Cl₂ used, its concentration in carrier gas and flow rate of carrier gas on the properties of carbosils has been defined. Adsorbents were characterized by: heats and isotherms of adsorption of n-hexane, benzene and chloroform, differential distribution of adsorption energy of n-hexane and specific surface area. Studies of the effect of the amount of carbon deposited on the silica surface area were carried out.     

Effect of surface modification with carbon-containing groups on the size, properties, and morphology of silica particles

We report the properties of hydrated silica surface-modified with aminopropyl, 3-(2-imidazolin-1-yl)propyl, or 1H,1H,2H,2H-perfluorodecyl. The modifier groups reside on the surface of the silica nanoparticles, as shown by NMR spectroscopy. We examine the effect of the nature and concentration of the modifier on the particle size and specific surface area of silica. Thermal analysis results demonstrate that the modified materials are stable up to 430°C.     

Grafting of LiAMPS on ethyl cellulose: a route to the fabrication of superior quality polyelectrolyte gels for rechargeable Lithium ion batteries

New types of semi-interpenetrating polymer gel electrolytes with high conductivity as well as strength for use in rechargeable Lithium polymer batteries are synthesized. Single ion conducting polyelectrolyte gels are made by first synthesizing grafted linear chains of Lithium salt of 2-acrylamido-2-methylpropane sulphonic acid on ethyl cellulose (EC) using free radical initiator azobis (cyclohexanecarbonitrile) in dimethyl acetamide solvent, then copolymerizing methyl methacrylate (MMA) and a crosslinking agent ethyleneglycol dimethacrylate to form semi-interpenetrating network. The effect of concentrations of EC and MMA on electrical conductivity and mechanical strength of gels are determined.     

Investigation of the effect of substrata on the surface free energy components of silica gel determined by thin layer wicking method

The components of surface free energy of silica gel deposited on glass plates, aluminium or plastic sheets (commercial Merck's plates for TLC) were determined by applying two theoretical approaches: the Lifshitz-van der Waals acid-base approach (LWAB), the geometric mean of apolar and polar interactions approach (GM). The thin layer wicking method was applied. Besides, from the measured contact angles of probe liquid (diiodomethane, -bromonaphthalene, water, formamide, glycerol and ethylene glycol) surface free energy components were calculated for the substrata on which the silica gel was deposited. In this case the equation of state (ES) was additional by applied. The study has shown that both the kind of substratum and that of the chambers used for measuring the penetration rate of the liquid do not influence the calculated values of the surface free energy components of silica gel. The components calculated from the two models of interfacial interactions: ^LW _s and ^AB _s or ^d _s and ^p _s appeared to be practically the same if diiodomethane and -bromonaphthalene were considered as weakly polar liquids, i.e. donor-acceptor interactions in the surface tension were taken into account. However, when _l ⁺ and _l ^– of these liquids are neglected, considerable differences occur, particularly in the determined value of Lifshitz-van der Waals component. The values of the total surface free energy of substrata calculated by applying three thermodynamic approaches are very similar, but if diiodomethane and -bromonaphthalene are considered as weakly polar liquids this similarity is more distinct.     

The selective effect of a constant magnetic field on the crystallization of flexible-chain polymers

A weak constant magnetic field produces a selective action upon crystallization of a high-molecular-mass poly(ethylene oxide) which is a model crystallizable flexible-chain polymer with polar units.