Immobilization Of Particles Research Articles

Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV–vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

Charge-Directed Immobilization of Bacteriophage on Nanostructured Electrode for Whole-Cell Electrochemical Biosensors.

A new type of carbon nanotube (CNT)-based impedimetric biosensing method has been developed for rapid and selective detection of live bacterial cells. A proof-of-concept study was conducted using T2 bacteriophage-based biosensors for electrochemical detection of Escherichia coli B. The T2 bacteriophage (virus) served as the biorecognition element, which was immobilized on polyethylenimine (PEI)-functionalized carbon nanotube transducer on glassy carbon electrode. Charge-directed, orientated immobilization of bacteriophage particles on carbon nanotubes was achieved through covalent linkage of phage capsid onto the carbon nanotubes. The presence of the immobilized phage on carbon nanotube-modified electrode was confirmed by fluorescence microscopy. Electrochemical impedance spectroscopy (EIS) was used to monitor the changes in the interfacial impedance due to the binding of E. coli B to T2 phage on the CNT-modified electrode. The detection was highly selective toward the B strain of E. coli as no signal was observed for the nonhost K strain of E. coli. The present achievable detection limit of the biosensor is 103 CFU/mL.

Enhancement of nanoscale zero-valent iron immobilization onto electrospun polymeric nanofiber mats for groundwater remediation

Abstract A new approach that combines nanoscale zero-valent iron (nZVI) with electrospinning technology has been put forward to avoid nZVI agglomeration and a secondary pollution. In this study, to enhance the immobilization of nZVI particles onto the polyacrylic acid (PAA)/polyvinyl alcohol (PVA) electrospun nanofiber mat, mats (M1, M2 and M3) with different PAA/PVA mass ratios (1:1, 2:1 and 3:1) were tested for the immobilization of nZVI particles and their performance of removing contaminants. The results indicate that M3 immobilized the most nZVI particles (48.4 wt% on the mat, ∼2.5 times the figure for previous study) and had the highest removals to methylene blue and Cu(II) ions at 94% and 83.6% respectively, resulting from more free carboxylic groups available on the cross-linked nanofibers as well as a higher porosity into the mat. Therefore, increasing the PAA/PVA ratio is effective to boost the performance of nZVI–PAA/PVA electrospun nanofiber mat, which has a great potential for the application of nZVI-targeted contaminants remediation.

Insulator-Based Dielectrophoresis As an Anti-Fouling Strategy for Nanoporous Silicon-Nitride Membrane Filters

Fouling of ultrathin nanoporous membrane significantly inhibits their use in purification, separation and miniaturized therapeutic devices. Dielectrophoresis (DEP) is an electrokinetic force that induces migration of a polarizable particle in an inhomogeneous electric field [1]. Application of DEP as an anti-fouling mechanism will enhance the membrane performance and service life without introducing harmful chemicals or stopping the filtration process [2]. However, the DEP force (FDEP ) on nanoparticles (NPs) is significantly reduced due to their small particle radius, as indicated in the equation below [1]: FDEP =2πεmr3Re[K(ω)]\U0001d6fb|\U0001d438|2 （1） where r is the particle radius, ω is the angular frequency, E is the root mean square electric field and Re[K(ω)] is the real part of the Clausius-Mossotti factor. Though applying larger voltage to increase \U0001d6fb|\U0001d438|2 can increase FDEP , this leads to undesirable consequences such as rapid joule heating and low energy efficiency. We hypothesized that by using ultrathin membranes, significant \U0001d6fb|\U0001d438|2 can be achieved without the need for extreme voltages. Our work aims to prove this concept by combining molecularly-thin nanoporous silicon-nitride (NPN) membrane filters with DEP and demonstrate successful repelling of nanoparticles from membrane surface (i.e. antifouling). This presentation will focus on testing our hypothesis by studying the effect of NPN geometry on FDEP . Numerical analyses using COMSOL Multiphysics® indicated that the thickness of NPN (~50 nm) can reduce the required voltage by 3-4 orders of magnitude compared to previous reports for similar insulator-based DEP-based NP manipulation [3,4,5]. We will also discuss our numerical analyses on the critical effect of pore density on NP rejection around the pore orifice. The presentation will also describe the microfluidic device developed for the experimental verification of the DEP-based NP rejection predicted by our theoretical studies. Using positively charged, fluorescein-labeled polystyrene NPs as a model foulant, we found that successful manipulation of NP trajectory above the NPN membrane can be achieved under a voltage bias of only 1V (compared to conventional voltage bias of ~1000V [1,4]). This simple, low-cost strategy offers a novel opportunity that combines DEP with ultrathin nanoporous membranes, enabling a potentially ground-breaking antifouling mechanism for ultrafiltration applications. Nakano, A.; Ros, A., Protein dielectrophoresis: Advances, challenges, and applications. Electrophoresis 2013, 34 (7), 1085-1096.Du, F.; Hawari, A.; Baune, M.; Thoming, J., Dielectrophoretically intensified cross-flow membrane filtration. Journal of Membrane Science 2009, 336(1-2), 71-78.Roberto C. Gallo-Villanueva, Michael B. Sano,Blanca H. Lapizco-Encinas, Rafael V. Davalos. Joule heating effects on particle immobilization in insulator-based dielectrophoretic devices. Electrophoresis 2014, 35, 352–361Nakano, A.; Chao, T. C.; Alanis, F. C.; Ros, A., Immunoglobulin G and bovine serum albumin streaming dielectrophoresis in a microfluidic device. Electrophoresis 2011, 32(17), 2314-2322.Asokan, S. B.; Jawerth, L.; Carroll, L. R.; Cheney, R. E.; Washburn, S.; Superfine, R., Two-dimensional manipulation and orientation of actin-myosin systems with dielectrophoresis. Nano Letter 2003 , 3(4), 431-437 Figure 1

Immobilization of mesoporous silica particles on stainless steel plates

A preliminary study aimed to the nano-engineering of stainless steel surface is presented. Aminopropyl-functionalized mesoporous silica is covalently and electrostatically anchored on the surface of stainless steel plates. The anchoring is carried out through the use of a nanometric spacer, and two different spacers are proposed (both below 2 nm in size). The first sample is obtained by anchoring to the stainless steel amino functionalized, a glutaryl dichloride spacer. This specie forms an amide linkage with the amino group while the unreacted acyl groups undergo hydrolysis giving a free carboxylic group. The so-obtained functionalized stainless steel plate is used as substrate for anchoring derivatized mesoporous silica particles. The second sample is prepared using 2-bromo-methyl propionic acid as spacer (BMPA). Successively, the carboxylic group of propionic acid is condensed to the aminopropyl derivatization on the external surface of the mesoporous silica particle through covalent bond. In both cases, a continuous deposition (coating thickness is around 10 μm) is obtained, in fact, XPS data do not reveal the metal elements constituting the plate. The nano-engineering of metal surfaces can represent an intriguing opportunity for producing long-term drug release or biomimetic surface.

Synthesis and characterization of chitosan/Mg-Al layered double hydroxide composite for the removal of oil particles from oil-in-water emulsion

The recovery of oil from oil-in-water emulsion has been investigated using chitosan/magnesium-aluminium layered double hydroxide hybrid composite (CS-LDHCs) by a single co-precipitation method. Resulting better adsorption efficiency of CS-LDHCs could be observed, indicating the synthesized material was effective to adsorb oil particles from oil-in-water emulsion at acidic pH (pH 3.0) than as-prepared LDH and raw chitosan. The enhancement of adsorption properties by CS-LDHCs material were attributed to the high content of LDH in chitosan, which makes the material more effective towards immobilization of oily particles. Batch experiment study has been elucidated by varying different physicochemical parameters such as time, pH, dose, initial oil concentration and temperature. The as-synthesized CS-LDHCs was characterized by various spectro analytical techniques viz., FTIR, SEM with EDAX, XRD, TGA and DSC analysis. To find out the best fit for the sorption process, the obtained adsorption equilibrium data was explained with Freundlich, Langmuir, Dubinin-Radushkevich and Tempkin isotherm models. The mechanism of adsorption process was demonstrated by calculating ΔG°, ΔH° and ΔS° values from thermodynamic parameters in order to understand the nature of sorption process. The schematic representation of oil removal using CS-LDHCs was explored in detail. This work provides an apparent proposal for the growth of oil removal technology.

Functionalization of cyclic olefin copolymer substrates with polyethylene glycol diacrylate for the in situ synthesis of immobilized nanoparticles

Nanoparticles as novel stationary phase could enhance chromatographic performance (efficiency and resolution). However, their implementation in columns is rather challenging. The methodological approach we propose is an in situ synthesis of such nanoparticles through photopolymerization of a miniemulsion containing hexyl acrylate monomers. While the miniemulsion composition was previously optimized, resulting in highly spherical monodisperse nanoparticles with a mean size inferior to 200 nm, the immobilization of such particles is not straightforward. The strategy consists in carrying out the miniemulsion polymerization in the very close vicinity of a reactive surface, namely cyclic olefin copolymer (COC), from which covalent bond can grow thanks to hydrogen abstraction. While the hydrophobic nature of COC appears to disturb the stability of the miniemulsion, a more polar surface allows simultaneous polymerization and anchoring of nanoparticles on the surface. Surface functionalization of COC with different monomers was tested in this work and polyethylene glycol dimethacrylate photografting was found to provide an adequate surface modification. It appears however that the extent of surface modification and especially the amount of initiator that is applied on the COC surface have consequences on both the spherical aspect and the number of resulting nanoparticles. An optimization of the PEGDA surface modification by central composite design in regards to PEGDA and BME amounts and irradiation time is proposed. SEM images after miniemulsion photopolymerization for different conditions of PEGDA photografting showed the impact of photografting on nanoparticle shape.

Physical properties of mixed Langmuir monolayers of polystyrene particles with poly(N,N-dimethylaminoethylmethacrylate) hairs and a poly(2-hydroxyethyl methacrylate) polymer at an air/water interface

The effect of adding a poly(2-hydroxyethyl methacrylate) (PHEMA) polymer to a Langmuir monolayer of polystyrene particles carrying poly(N,N-dimethylaminoethylmethacrylate) hair (PDMA-PS particles) at air/water interfaces on the physical properties of the monolayer was studied. The addition of PHEMA to a PDMA-PS particle monolayer at an air/water interface gave a polymer-like monolayer at low surface pressures and a particle-like monolayer at high surface pressures. The PDMA-PS particles formed small aggregates that were dispersed throughout the PHEMA monolayer at low surface pressures, a result suggesting that the particles were trapped in the PHEMA network. Monolayers of closely packed particles were observed at higher surface pressures, suggesting that PHEMA was squeezed-out at higher surface pressures. The stiffness of the mixed monolayer was independent of the surface pressure, but increased as the ratio of PHEMA in the mixed monolayer increased. This increased stiffness was explained by the immobilization of the PDMA-PS particles by PHEMA.

Immobilization of catalytic virus-like particles in a flow reactor.

A functional microfluidic reactor is constructed by the immobilization of gold containing virus-based protein cages that catalyze the reduction of nitro-arenes with high efficiency.

Extending the limits of direct force measurements: colloidal probes from sub-micron particles.

Direct force measurements by atomic force microscopy (AFM) in combination with the colloidal probe technique are widely used to determine interaction forces in colloidal systems. However, a number of limitations are still preventing a more universal applicability of this technique. Currently, one of the most significant limitations is that only particles with diameters of several micrometers can be used as probe particles. Here, we present a novel approach, based on the combination of nanofluidics and AFM (also referred to as FluidFM-technique), that allows to overcome this size limit and extend the size of suitable probe particles below diameters of 500 nanometers. Moreover, by aspiration of colloidal particles with a hollow AFM-cantilever, the immobilization process is independent of the particle's surface chemistry. Furthermore, the probe particles can be exchanged in situ. The applicability of the FluidFM-technique is demonstrated with silica particles, which are also the types of particles most often used for the preparation of colloidal probes. By comparing 'classical' colloidal probes, i.e. probes from particles irreversibly attached with glue, and various particle sizes aspirated by the FluidFM-technique, we can quantitatively evaluate the instrumental limits. Evaluation of the force profiles demonstrate that even for 500 nm silica particles the diffuse layer properties can be evaluated quantitatively. Therefore, direct force measurements on the level of particle sizes used in industrial formulations will become available in the future.

Photoresponsive, reversible immobilization of virus particles on supramolecular platforms

Here we report on the covalent attachment of photoresponsive azobenzene moieties to cowpea chlorotic mottle virus (CCMV). The modified virus capsids can be reversibly immobilized on cucurbit[8]uril (CB[8]) bearing surfaces via supramolecular complexation.

Fe/TiO2 composite coatings modified by ceria layer: Electrochemical synthesis using environmentally friendly methanesulfonate electrolytes and application as photocatalysts for organic dyes degradation

This work reports the results of our effort to manufacture Fe/TiO2 electrodeposited composite coatings modified by ceria layer and use them as heterogeneous photocatalysts for the decomposition of some organic dyes. Iron electrodeposited matrix may be a cheap, available, nontoxic and easily repairable support for TiO2 photocatalysts, however, it is not corrosion-resisting enough. In order to improve the corrosion stability, as-deposited Fe/TiO2 (5%wt. of titania) composite coatings obtained from a methanesulfonate iron plating bath were modified by cathodic treatment in solution containing cerium (III) methanesulfonate. As a result, a very thin layer of cerium oxides was formed on the surface of Fe matrix. The corrosion resistance of iron/titania coatings after their modification by ceria film was studied by means of voltammetry method and electrochemical impedance spectroscopy. The surface modification of Fe/TiO2 composites by ceria layer resulted in a significant increase in their corrosion stability which allows their practical application as photocatalysts for wastewater treatment. The photocatalytic properties of TiO2 particles immobilized on Fe/TiO2 composite electrodeposits modified by ceria layers were tested in the reaction of photochemical degradation of methyl orange (MO) and methylene blue (MB) dyes in water under the action of UV radiation. The apparent rate constants of MO and MB photodegradation at natural pH values were 0.0018 and 0.0056min−1, respectively. Thus we developed a new technique of TiO2 particles immobilization for advanced oxidation processes, which involves electrodeposited composite coatings with Fe matrix.

RETRACTED: Preparation of granulated N-doped TiO2/diatomite composite and its applications of visible light degradation and disinfection

Abstract The industrial application of TiO 2 as photocatalyst is still limited due to its low reusability and requirement for UV light. For this reason, we combined nitrogen-doping with particle immobilization to prepare granulated N-doped TiO 2 /diatomite (GNTD) composite for both water treatment and bacteria inactivation. Pretreated diatomite was found to be a good TiO 2 supporter, due to its high adsorption capability to enrich target molecules around TiO 2 nanoparticles, which improves its photo-oxidation efficiency, and granulation increases its recoverability. Kinetic studies indicated that GNTD catalyst showed good degradation capability towards Rhodamine B ( RhB ) under visible light irradiation. It also demonstrated its superior ability to inactivate bacteria, including gram-positive Staphylococcus aureus ( S. aureus ) and gram-negative Escherichia coli ( E. coli ). Characterization results show that TiO 2 nanoparticles were immobilized onto the surface of diatomite via chemical bonding. Moreover, GNTD composite could be simply recycled for reuse, and still showed stable photo-activity. All these advantages of GNTD composite prove itself as a promising material for industrial applications.

Anti-PEG antibodies alter the mobility and biodistribution of densely PEGylated nanoparticles in mucus.

Antibodies that specifically bind polyethylene glycol (PEG) can lead to rapid elimination of PEGylated therapeutics from the systemic circulation. We have recently shown that virus-binding IgG can immobilize viruses in mucus via multiple low-affinity crosslinks between IgG and mucins. However, it remains unclear whether anti-PEG antibodies in mucus may also alter the penetration and consequently biodistribution of PEGylated nanoparticles delivered to mucosal surfaces. We found that both anti-PEG IgG and IgM can readily bind nanoparticles that were densely coated with PEG polymer to minimize adhesive interactions with mucus constituents. Addition of anti-PEG IgG and IgM into mouse cervicovaginal mucus resulted in extensive trapping of mucus-penetrating PEGylated nanoparticles, with the fraction of mobile particles reduced from over 95% to only 34% and 7% with anti-PEG IgG and IgM, respectively. Surprisingly, we did not observe significant agglutination induced by either antibody, suggesting that particle immobilization is caused by adhesive crosslinks between mucin fibers and IgG or IgM bound to individual nanoparticles. Importantly, addition of corresponding control antibodies did not slow the PEGylated nanoparticles, confirming anti-PEG antibodies specifically bound to and trapped the PEGylated nanoparticles. Finally, we showed that trapped PEGylated nanoparticles remained largely in the luminal mucus layer of the mouse vagina even when delivered in hypotonic formulations that caused untrapped particles to be drawn by the flow of water (advection) through mucus all the way to the epithelial surface. These results underscore the potential importance of elucidating mucosal anti-PEG immune responses for PEGylated therapeutics and biomaterials applied to mucosal surfaces. PEG, generally considered a 'stealth' polymer, is broadly used to improve the circulation times and therapeutic efficacy of nanomedicines. Nevertheless, there is increasing scientific evidence that demonstrates both animals and humans can generate PEG-specific antibodies. Here, we show that anti-PEG IgG and IgM can specifically immobilize otherwise freely diffusing PEG-coated nanoparticles in fresh vaginal mucus gel ex vivo by crosslinking nanoparticles to the mucin mesh, and consequently prevent PEG-coated nanoparticles from accessing the vaginal epithelium in vivo. Given the increasing use of PEG coatings to enhance nanoparticle penetration of mucosal barriers, our findings demonstrate that anti-PEG immunity may be a potential concern not only for systemic drug delivery but also for mucosal drug delivery.

Immobilization of Colloidal Monolayers at Fluid⁻Fluid Interfaces.

Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle spacing can be formed, as required, for instance, in surface patterning and sensing applications. At the same time, the immobilization of particles locked into desired structures to be transferred to solid substrates remains challenging. Here, we describe three different strategies to immobilize monolayers of polystyrene microparticles at water–decane interfaces. The first route is based on the leaking of polystyrene oligomers from the particles themselves, which leads to the formation of a rigid interfacial film. The other two rely on in situ interfacial polymerization routes that embed the particles into a polymer membrane. By tracking the motion of the colloids at the interface, we can follow in real-time the formation of the polymer membranes and we interestingly find that the onset of the polymerization reaction is accompanied by an increase in particle mobility determined by Marangoni flows at the interface. These results pave the way for future developments in the realization of thin tailored composite polymer-particle membranes.

Surface Functionalization of Natural Rubber by UV‐Induced Thiol‐ene Chemistry

SummaryNatural rubber (NR) surfaces with tailored physicochemical properties and spatially controlled surface topology were prepared by exploiting radical‐mediated thiol‐ene chemistry. Selected functional thiols were immobilized onto NR surfaces by the photo‐induced addition reaction across the unsaturated CC double bonds of the cis‐1,4‐isoprene units. The modified elastomer surfaces are characterized by means of ATR FTIR spectroscopy to follow changes in the chemical surface composition, and by contact angle measurements to study changes in surface polarities. The results evidence the versatility of this photochemical functionalization route since different surface characteristics and surface reactivities were obtained, depending on the chemical nature of the attached thiol. In addition, the influence of the surface functionalization on bulk properties and surface morphology was determined by tensile tests and microscopic techniques, respectively. Results show that both tensile properties and surface morphology are not affected by the photochemical functionalization process. The immobilized thiols were further used as reactive anchor groups for a subsequent immobilization of inorganic silica particles, resulting in a well‐defined change in surface roughness and topology. Spatial control of surface properties was accomplished by photolithographic techniques that enabled a patterned immobilization of inorganic particles onto NR surfaces. Microscopic techniques revealed the selective coupling of the inorganic particles in the illuminated surface areas that were defined by high resolution and clear edges.

Measurement and modeling of engineered nanoparticle transport and aging dynamics in a reactive porous medium

AbstractA continuous time random walk particle tracking (CTRW‐PT) method was employed to model flow cell experiments that measured transport of engineered nanoparticles (ENPs) in a reactive porous medium. The experiments involved a water‐saturated medium containing negatively charged, polyacrylamide beads, resembling many natural soils and aquifer materials, and having the same refraction index as water. Negatively and positively charged ENPs were injected into a uniform flow field in a 3‐D horizontal flow cell, and the spatial and temporal concentrations of the evolving ENP plumes were obtained via image analysis. As a benchmark, and to calibrate the model, Congo red tracer was employed in 1‐D column and 3‐D flow cell experiments, containing the same beads. Negatively charged Au and Ag ENPs demonstrated migration patterns resembling those of the tracer but were slightly more dispersive; the transport was well represented by the CTRW‐PT model. In contrast, positively charged AgNPs displayed an unusual behavior: establishment of an initial plume of essentially immobilized ENPs, followed by development of a secondary, freely migrating plume. The mobile plume was found to contain ENPs that, with aging, exhibited aggregation and charge inversion, becoming negatively charged and mobile. In this case, the CTRW‐PT model was modified to include a probabilistic law for particle immobilization, to account for the decreasing tendency (over distance and time) of the positively charged AgNPs to attach to the porous medium. The agreement between experimental results and modeling suggests that the CTRW‐PT framework can account for the non‐Fickian and surface‐charge‐dependent transport and aging exhibited by ENPs in porous media.

Electron Microscopy: Impact of Membrane‐Induced Particle Immobilization on Seeded Growth Monitored by In Situ Liquid Scanning Transmission Electron Microscopy (Small 20/2016)

Electron Microscopy: Impact of Membrane‐Induced Particle Immobilization on Seeded Growth Monitored by In Situ Liquid Scanning Transmission Electron Microscopy (Small 20/2016)

Poly(vinyl alcohol) and alginate cross-linked matrix with immobilized Prussian blue and ion exchange resin for cesium removal from waters

Cesium (Cs) removal from contaminated water bodies is an emerging issue after the disaster at the Fukushima Daiichi Nuclear Power Plant. The Prussian blue (PB) is an effective Cs adsorbent but will release hexacyanoferrate fragments from the adsorbent matrix during adsorption. Alginate is an affordable biopolymer for PB particles immobilization. This study synthesized poly(vinyl alcohol) (PVA) and alginate cross-linked matrix for immobilization of PB nano-sized particles and a surface-modified styrene–ethyl styrene divinyl benzene resin and tested their swelling stability and Cs adsorption performance in fresh water and in seawater. The PVA–alginate granules have high structural stability in both fresh water and seawater, with the Cs adsorption capability higher for the former than the latter. The adopted resin effectively remove released PB fragments from the tested granules. The transport and reaction parameters for the granules and for the sand filter bed were estimated.

Impact of Membrane-Induced Particle Immobilization on Seeded Growth Monitored by In Situ Liquid Scanning Transmission Electron Microscopy.

In situ liquid cell scanning transmission electron microscopy probes seeded growth in real time. The growth of Pd on Au nanocubes is monitored as a model system to compare growth within a liquid cell and traditional colloidal synthesis. Different growth patterns are observed due to seed immobilization and the highly reducing environment within the liquid cell.