Detection of protein coatings on nanoparticles surfaces by ToF‐SIMS and advanced electron microscopy

In this study, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and advanced electron microscopy (scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM)) were applied to detect and analyse different nano‐scaled protein coatings on gold nanoparticles (NP). The NP were coated with collagen type I and fibronectin as well as different combinations of these proteins. These two main proteins in human cell organization and tissue formation were identified with the aid of ToF‐SIMS by typical amino acid mass peak detection. In addition, the protein‐coated particles were investigated by TEM and SEM to get information about the protein structure, the protein layer thickness on the particle surfaces and the reaction of NP in different protein solutions. In this study, a differentiation of diverse protein induced particle agglomeration was proven. The investigations of this study were part of the Specific Targeted Research Project CellNanoTox (project no. NMP4‐CT‐2006‐032731) funded by the European Commission under the 6th EU Framework Programme for Research and Technological Development. Copyright © 2013 John Wiley & Sons, Ltd.     

Polyvinylimidazole/sol–gel composite as a novel solid‐phase microextraction coating for the determination of halogenated benzenes from aqueous solutions

A polyvinylimidazole/sol–gel composite is proposed as a novel solid‐phase microextraction fiber to extract five halobenzenes from the headspace of aqueous solutions in combination with gas chromatography with mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The obtained results showed that porous polyvinylimidazole/sol–gel composite was chemically deposited on fused silica fiber. The effect of important extraction parameters including extraction temperature, extraction time, and salt content were investigated. The optimum conditions were as follows: extraction temperature 25°C, extraction time 20 min, and salt concentration 30 w/v%. Detection limits and relative standard deviations of the developed method for halogenated benzenes were below 0.1 pg/mL and 15%, respectively. Repeatability of the proposed method, explained by relative standard deviation, varied between 5.48 and 9.15% (n = 5). The limits of detection (S/N = 3) ranged between 0.01 and 0.10 ng/L using gas chromatography with mass spectrometry with selected ion monitoring mode. For real sample analysis, three types of water samples with different matrices (ground, surface, and tap water) were studied. The optimized procedure was applied to extraction and method validation of halogenated benzenes in spiked water samples.     

Characterization of chromate conversion coating on AA7075‐T6 aluminum alloy

Chromate conversion coatings (CCCs) on AA7075‐T6 were characterized using scanning electron microscopy, focused ion beam sectioning and scanning transmission electron microscopy with nano‐electron dispersive spectroscopy line profiling. The thickness and composition of the CCC was different at different locations on the heterogeneous microstructure of AA7075‐T6. The coating formed on the matrix phase was much thicker than that formed on the coarse Al–Cu–Mg, Al–Fe–Cu and Mg–Si intermetallic particles. Nano‐electron dispersive spectroscopy line profiling indicated that the coating on the Al–Fe–Cu particles was similar to the CCC formed on the phase matrix, primarily a chromium oxide. However, the coatings on the Al–Cu–Mg and Mg–Si particles were mixed Al/Mg/Cr oxide and Mg oxide, respectively. The growth of CCC followed a linear‐logarithmic kinetic rate law. The observations of this study support the sol‐gel model of CCC formation. Copyright © 2004 John Wiley & Sons, Ltd.     

Multifunctional superhydrophobic/oleophobic and flame-retardant cellulose fibres with improved ice-releasing properties and passive antibacterial activity prepared via the sol–gel method

In this research, a two-component sol–gel inorganic–organic hybrid coating was prepared on a cotton fibre surface. An equimolar sol mixture of the precursors 1H,1H,2H,2H-perfluorooctyltriethoxysilane (SiF) and P,P-diphenyl-N-(3-(trimethoxysilyl)propyl) phosphinic amide (SiP) was applied to cotton fabric samples using the pad-dry-cure method. The surfaces of the untreated and coated cotton fibres were characterised using scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight-secondary ion mass spectrometry. The functional properties of the coated cotton fabric samples were investigated using static contact angle measurements with water and n-hexadecane, the ice-releasing test, antibacterial testing against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, thermogravimetric analysis in an air atmosphere, and vertical flammability tests. The results reveal the formation of a nanocomposite two-component inorganic–organic hybrid polymer network that is homogenously distributed over the cotton fibre surface. The presence of the SiP component in the two-component inorganic–organic hybrid coating did not hinder the functional properties imparted by the presence of the SiF component and vice versa, illustrating their compatibility. The cooperative action of the SiF and SiP components in the two-component coating provided the cotton fabric with exceptional multifunctionality, including simultaneous superhydrophobicity and high oleophobicity, passive antibacterial activity, and improved thermo-oxidative stability.     

Cluster TOF‐SIMS imaging of human skin remains: analysis of a South‐Andean mummy sample

A skin sample from a South‐Andean mummy dating back from the XI^th century was analyzed using time‐of‐flight secondary ion mass spectrometry imaging using cluster primary ion beams (cluster‐TOF‐SIMS). For the first time on a mummy, skin dermis and epidermis could be chemically differentiated using mass spectrometry imaging. Differences in amino‐acid composition between keratin and collagen, the two major proteins of skin tissue, could indeed be exploited. A surprising lipid composition of hypodermis was also revealed and seems to result from fatty acids damage by bacteria. Using cluster‐TOF‐SIMS imaging skills, traces of bio‐mineralization could be identified at the micrometer scale, especially formation of calcium phosphate at the skin surface. Mineral deposits at the surface were characterized using both scanning electron microscopy (SEM) in combination with energy‐dispersive X‐ray spectroscopy and mass spectrometry imaging. The stratigraphy of such a sample was revealed for the first time using this technique. More precise molecular maps were also recorded at higher spatial resolution, below 1 µm. This was achieved using a non‐bunched mode of the primary ion source, while keeping intact the mass resolution thanks to a delayed extraction of the secondary ions. Details from biological structure as can be seen on SEM images are observable on chemical maps at this sub‐micrometer scale. Thus, this work illustrates the interesting possibilities of chemical imaging by cluster‐TOF‐SIMS concerning ancient biological tissues. Copyright © 2012 John Wiley & Sons, Ltd.     

Studies on the oxygen sensitivity and microstructure of sol–gel based organic–inorganic hybrid coatings doped with platinum porphyrin dye

Hybrid organic–inorganic nanocomposite coatings were prepared by copolymerizing tetraethylorthosilicate with ethyltriethoxysilane with an acid catalysis process. Oxygen sensor coatings were fabricated by doping the hybrid sol with platinum meso-tetra(pentfluorophenyl) porphyrin. Photophysical properties and oxygen sensitivity of the sensor coatings were studied. The microstructure of the coatings was examined using optical microscopy and scanning electron microscopy. The effect of sol–gel process conditions like precursor silane molar ratio, acid concentration and stirring time of the sol on the oxygen sensitivity and surface microstructure of the sensor coating was studied. Oxygen sensitivity and surface morphology of the coatings were dependent on the sol–gel process parameters.     

Hybrid silica coatings on polycarbonate: enhanced properties

Hybrid silica coatings based on 3- glycidoxypropyltriethoxysilane (GPTES), tetraethylorthosilicate (TEOS) and colloidal silica were deposited on polycarbonate (PC) by the sol–gel method, in order to obtain a material with enhanced properties with respect to raw PC (mainly scratch resistance, hydrophobicity and density), and consequently reach increased durability. The necessity of performing a N₂-plasma treatment on PC (before coating deposition) was highlighted in order to obtain a good adherence between the coating and the substrate: XPS measurements showed that after treatment, nitrogenous radicals had formed on the PC surface and were able to link covalently with the sol during its deposition. Adherence was also higher when young sols (<8-day-old) were used. Different alkoxysilanes/colloidal silica ratios were tested to optimize the coating resistance: crack resistance of the coatings was found to be greater when the ratio was high. Scratch resistance of raw PC was enhanced as soon as PC was coated, irrespective of the alkoxysilanes/colloidal silica ratio or the sol ageing time. The density of the coatings was assessed by environmental ellipsometric porosimetry and found to be very high. Water contact angle measurements showed that the hydrophobicity of the coatings was inferior to raw PC. The addition in the sol of a small wt% of octyltriethoxysilane (OTES), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FTES) and silicone surface additive (BYK-306) allowed a significant increase in hydrophobicity of the samples.     

Effect of monomer structures and preparation methods on the morphology and properties of UV cured organic–inorganic hybrid films

The effects of preparation methods and monomer chemical structures on the microstructure, morphology, and properties of the hybrid films were studied. 7DBPA‐3S was synthesized by the sol–gel reaction of precondensed silica particles with alkoxysilane‐modified polymers DBPA. DBP‐POBG3T3 was prepared by the radiation curing of comb‐like UV curable alkoxysilanes POBG3T3 with UV curable polymer DBP, followed by the sol–gel reaction of alkoxysilanes. The DBP‐POBG3T3 film consisted of polymer matrix and large tethered aggregates with tiny silica connected by organic chains. On the contrary, silica nanoparticles were well‐dispersed in the 7DBPA‐3S hybrid film. The TEM, energy dispersive X‐ray Si‐mapping and P‐mapping images are good experimental approaches to characterize the texture of the tethered aggregates. The 7DBPA‐3S hybrid composite with well‐dispersed silica nanoparticles exhibited smoother surface, higher transparency, and better thermal stability than the DBP‐POBG3T3 composite did. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1152–1165, 2007     

Wood surface protection with different alkoxysilanes: a hydrophobic barrier

This paper describes coatings on wood surfaces made by dipping the wood into solutions of different alkoxysilanes. The silanes used as precursors contain different organic groups [R’Si(OR’’)]. These materials tend to deposit as inorganic–organic polymeric films, where the organic groups (aliphatic hydrocarbons, fluorinated hydrocarbons or aromatic substituents) show hydrophobic properties, which reduce the wettability of the surface. The effects of these treatments on the wood surface were extensively studied using various analytical techniques: scanning electron microscopy with energy dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, water contact angle measurements, and flame resistance tests. The resulting data show that the chemical treatment changes the wood’s surface energy, reducing its wettability and reaction to fire. The main innovative finding of this research is that the coatings obtained from a cheaper precursor have a similar performance to that of the more expensive precursors normally used.     

Rational Design of Ag/TiO2 Nanosystems by a Combined RF‐Sputtering/Sol‐Gel Approach

The present work is devoted to the preparation of Ag/TiO₂ nanosystems by an original synthetic strategy, based on the radio‐frequency (RF) sputtering of silver particles on titania‐based xerogels prepared by the sol–gel (SG) route. This approach takes advantage of the synergy between the microporous xerogel structure and the infiltration power characterizing RF‐sputtering, whose combination enables the obtainment of a tailored dispersion of Ag‐containing particles into the titania matrix. In addition, the system′s chemico‐physical features can be tuned further through proper ex situ thermal treatments in air at 400 and 600 °C. The synthesized composites are extensively characterized by the joint use of complementary techniques, that is, X‐ray photoelectron and X‐ray excited Auger electron spectroscopies (XPS, XE‐AES), secondary ion mass spectrometry (SIMS), glancing incidence X‐ray diffraction (GIXRD), field emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM), electron diffraction (ED), high‐angle annular dark field scanning TEM (HAADF–STEM), energy‐filtered TEM (EF–TEM) and optical absorption spectroscopy. Finally, the photocatalytic performances of selected samples in the decomposition of the azo‐dye Plasmocorinth B are preliminarily investigated. The obtained results highlight the possibility of tailoring the system characteristics over a broad range, directly influencing their eventual functional properties.     

A sol–gel polymerization method for creating nanoporous polyimide silsesquioxane nanostructures as soft dielectric materials

A sol–gel polymerization method was developed to make polyimide (PI) silsesquioxane (SSQ) nanoparticles as functional, soft dielectric materials. The surface functionalization of the polymer chain backbone and chain ends of poly(trimellitic anhydride chloride‐co‐4,4′‐methylenedianiline), PMR‐15 resin, with para‐(chloromethyl)‐phenylethyltrimethoxy silane yielded a novel sol–gel reactive sites functionalized PMR‐silane precursor. Upon base‐catalyzed hydrolysis and condensation of the PMR‐silane precursor, spherical, raspberry‐like PMR‐SSQ nanoparticles were obtained in considerably good yield. Controlling the particle size distribution was attempted upon adjusting the molar ratio between the silane precursor and the base, as well as in the presence of a catalytic amount of silica sols. Particle composition, thermal stability, and morphology were confirmed from Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy analyses. Nanoparticles, visualized under transmission electron microscopy exhibit a nanoporous structure. The Brunauer–Emmett–Teller analysis confirmed that the average pore dimension is ranged from 2 to 5 nm. The dielectric constant of PMR‐SSQ nanoparticles was as low as 1.95, compared to dielectric constants of 3.05 and 3.13 for PMR‐15 and PMR‐silane, respectively. Thus, the base‐catalyzed sol–gel polymerization of alkoxysilylated PI offers a novel synthetic path to make functional nanoporous PI nanostructures that possess ultralow dielectric constants. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 57, 562–571.     

Pentamethylcyclopentadienylrhodium(I) complexes incorporated into porous polysiloxanes prepared by a sol–gel process: catalysts for hydrogenation of crotonic acid in water

Pentamethylcyclopentadiene‐functionalized polysiloxanes were prepared by a sol–gel process from tetraethoxysilane and (pentamethylcyclopentadienylmethyl)methyldiethoxysilane without a catalyst. The polysiloxanes are microporous–mesoporous solids, of which the BET surface areas and micropore volumes are inversely proportional to the concentration of the functionalizing agent (5–21 mol%) in the starting mixture of alkoxysilanes. The polysiloxanes were also characterized by CP MAS ¹³C NMR spectroscopy, revealing essentially the same structure of organofunctional ligand as that in particulate materials with low surface areas prepared earlier in a sol–gel process catalyzed by dibutyltin diacetate. Novel alkoxysilyl‐substituted pentamethylcyclopentadienyl (1,5‐cyclo‐octadiene)rhodium(I) complexes were synthesized from the corresponding cyclopentadienes by deprotonation followed by reaction with [(cod)RhCl]₂ (cod = cyclo‐octadiene). Polysiloxane‐bound rhodium complexes were prepared by a sol–gel reaction analogous to the one mentioned above and were found to catalyze the hydrogenation of crotonic acid in water; to the best of our knowledge, this constitutes the first example of catalysis by a well‐defined polysiloxane‐bound transition metal complex in an aqueous system. Copyright © 2000 John Wiley & Sons, Ltd.     

Crack‐free sol‐gel coatings for protection of AA1050 aluminium alloy

Organically modified sol‐gel coatings have been investigated as potential replacements for chromate conversion treatments of an AA1050 aluminium alloy. The coatings were prepared by combination of a completely hydrolysable precursor of tetra‐n‐propoxyzirconium (TPOZ), with a partially hydrolysable precursor of glycidoxypropyltrimethoxysilane (GPTMS). GPTMS contains an organic functional group, which is retained in the sol‐gel coatings after the hydrolysis–condensation process. Different GPTMS/TPOZ ratios and withdrawal speeds were studied. Coatings produced using a low GPTMS/TPOZ ratio and a high withdrawal speed generated significant cracks due to the shrinkage of the coatings, with no corrosion protection of the alloy. It was found that increase of organic moieties reduced the shrinkage of the coatings and the tendency for crack formation. By control of process parameters and ratios of organic and inorganic moieties, crack‐free sol‐gel coatings above 1 µm thick, with improved corrosion protection, can be produced on the alloy surface. Copyright © 2010 John Wiley & Sons, Ltd.     

Use of computational modeling in preparation and evaluation of surface imprinted xerogels for binding tetracycline

Microchimica Acta - Linear alkyl alkoxysilanes (methoxy and ethoxy-based) of varying length were used in preparing tetracycline surface imprinted silica xerogels by the sol–gel process. The...     

Time‐of‐flight secondary ion mass spectrometry and gas chromatography–mass spectrometry studies of alkanethiol self‐assembled monolayers on nanoporous gold surfaces

The dimerization of alkanethiol mixtures (hexanethiol, octanethiol, and dodecanethiol) to form self‐assembled monolayers (SAMs) from headspace on nanoporous gold surfaces was studied for the first time using gas chromatography (GC/MS) and time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS). The nanoporous gold surfaces were obtained by an acidic etching of a 585‐gold alloy. Field emission scanning electron microscopy (FE‐SEM) was utilized to study the change of the surface geometry and porosity of the gold surfaces before and after etching. Alkanethiols were deposited from the vapor phase above the thiol solutions (headspace) on nanoporous gold plates and nanoporous gold solid‐phase vmicroextraction (SPME) fibers. The nanoporous gold substrates were analyzed by TOF‐SIMS and GC/MS, respectively. The TOF‐SIMS spectra exhibited various gold–sulfur ion clusters and specific peaks related to the adsorption of thiols such as deprotonated monomers, thiolate–Au, dimers (e.g., dialkyl sulfides–Au and dialkyl disulfides–Au). The GC/MS analysis of headspace extractions of alkanethiol mixtures by nanoporous gold SPME fibers showed a high extraction efficiency of alkanethiol, dialkyl sulfide, and dialkyl disulfide when compared with the commercial SPME fibers (DVB‐CAR‐PDMS and CAR‐PDMS). Different GC/MS optimization factors were studied including the extraction time and desorption temperature.     

X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry characterization of aging effects on the mineral fibers treated with aminopropylsilane and quaternary ammonium compounds

X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry were used to investigate the aging effects on the aminopropylsilane (APS) and quaternary ammonium surfactant‐treated mineral fibers. APS‐coated mineral fiber samples were treated with cationic surfactant and mineral oil and aged at 70 °C temperature and 95% humidity. From quantitative XPS measurements, an increase in the atomic composition of oxygen, nitrogen, and silicon is observed after aging. An increase in the protonated amino groups in the N1s high‐resolution spectra and C–N group in the C1s high‐resolution spectra is also observed. These results indicate that the concentration of hydrocarbon groups decreases after aging due to the partial removal of the long hydrocarbon chains of the surfactant and mineral oil and/or hydrolysis and segregation of APS to the fiber surface. The principal component analysis (PCA) was applied to the time‐of‐flight secondary ion mass spectrometry spectra, and an increase in the intensities of APS characteristic peaks were observed after aging. The observed increase in the signals of APS originates from underlying silanized fibers after the removal of the surfactant and mineral oil from the surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Polyimide–silica hybrid coatings: morphological,mechanical, and thermal investigations

In this study, polyimide–silica (PI–silica) based hybrid coating compositions were prepared from tetraethoxysilane (TEOS), γ‐glycidyloxypropyl trimethoxy silane (GOTMS), and polyamic acid (PAA) via a combination of sol–gel and thermal imidization techniques. PAA was synthesized from 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) and 3,3'‐Diaminodiphenyl sulfone (DDS) in N‐Methyl‐2‐pyrrolidone (NMP). The silica content in the hybrid coatings was varied from 0 to 20 wt%. The structural characterization of the hybrid coatings was performed using FTIR and ²⁹Si‐NMR spectroscopies. Results from both pendulum hardness and micro indentation test show that the hardness of hybrid coatings improves with the increase in silica content. The tensile tests also demonstrated that the mechanical properties at low silica content are rather striking. Their surface morphologies were characterized by scanning electron microscopy (SEM). SEM studies revealed that inorganic particles were distributed homogenously through the PI matrix. It was also found that, incorporation of the silica domains increased the thermal stability of the hybrid coatings. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and application of chlorpyrifos molecularly imprinted solid‐phase microextraction probes for the residual determination of organophosphorous pesticides in fresh and dry foods

A solid‐phase microextraction probe was prepared on the surface of a stainless‐steel wire through molecular sol–gel imprinting technology using chlorpyrifos as a template molecule, tetraethoxysilane as a sol–gel precursor, and acrylamide and β‐cyclodextrin as functional monomers. The polymer was characterized by infrared spectrometry and scanning electron microscopy. Moreover, the selectivity and the parameters including the type and volume of the extraction solvents, ionic strength, pH, temperature, extraction time, stirring speed, and desorption time affecting extraction performance were evaluated. Under the optimum solid‐phase microextraction and gas chromatography conditions, the linear ranges were 0.25–25.0 μg/L for chlorpyrifos, quinalphos, triazophos, pirimiphos‐methyl, and chlorpyrifos‐methyl with the correlation coefficient above 0.99. The detection limits (S/N = 3) were in the range of 0.02–0.07 μg/L and the RSDs were <7.3%. The developed method was successfully used to determine the multi‐residues of chlorpyrifos, quinalphos, triazophos, pirimiphos‐methyl, and chlorpyrifos‐methyl in green peppers and cinnamon with satisfactory recoveries.     

Nanoscale imaging of Li and B in nuclear waste glass,a comparison of ToF‐SIMS,NanoSIMS, and APT

It has been very difficult to use popular elemental imaging techniques to image Li and B distribution in glass samples with nanoscale resolution. In this study, time‐of‐flight secondary ion mass spectrometry, nanoscale secondary ion mass spectrometry, and atom probe tomography (APT) were used to image the distribution of Li and B in two representative glass samples, and their performance was comprehensively compared. APT can provide three‐dimensional Li and B imaging with very high spatial resolution (≤2 nm). In addition, absolute quantification of Li and B is possible, although there remains room for improving accuracy. However, the major drawbacks of APT include poor sample compatibility and limited field of view (normally ≤100 × 100 × 500 nm³). Comparatively, time‐of‐flight secondary ion mass spectrometry and nanoscale secondary ion mass spectrometry are sample‐friendly with flexible field of view (up to 500 × 500 µm² and image stitching is feasible); however, lateral resolution is limited to only about 100 nm. Therefore, secondary ion mass spectrometry and APT can be regarded as complementary techniques for nanoscale imaging of Li and B in glass and other novel materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface characterization of pre‐formed alginate fibres incorporated with a protein by a novel entrapment process

A novel physical entrapment process has been explored as an approach to surface incorporation of proteins within pre‐formed alginate fibres under mild conditions. Entrapment of the protein of choice was achieved by exposing the alginate fibres to a Na⁺‐rich NaCl/CaCl₂ mixture solution, which caused the formation of a moderate dissociation layer into which the protein could diffuse. Subsequent addition of a large excess of multi‐valent cations led to the collapse of the surface and entrapment of the protein within the surface. Bovine serum albumin (BSA) was used as a model protein to investigate the effect of process parameters on the entrapment efficiency. Scanning electron microscopy revealed that there was an increase in the surface roughness and a slight increase in the average diameter of the fibres after protein entrapment. The presence of the protein at the surface of alginates after the entrapment process was confirmed by means of confocal laser‐scanning microscopy, X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The ion exchanges at the surface were evident, as detected by XPS and ToF‐SIMS. It was found that under fixed pre‐swelling conditions, the entrapment efficiency increased with increasing treatment time and, particularly, with protein concentration in the exposure solution. Copyright © 2005 John Wiley & Sons, Ltd.