Search

Pattern Replication in Blends of Semiconducting and Insulating Polymers Casted by Horizontal Dipping

To provide complete characterization of immunoassay on silicon biosensor surfaces, atomic force microscopy, (angle-resolved) X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were applied to examine Si 3 N 4 surfaces modified with (3-aminopropyl)triethoxysilane, coated with gamma globulins (IgG), blocked with bovine serum albumin and then reacted with anti-IgG antibody for two complementary pairs (rabbit and mouse IgG) at various concentrations (from 0.3 nM to 330 nM). Protein coverage, as reflected in (amine to total N1s) XPS signal ratio and determined from ARXPS, decreases slightly due to blocking and then increases monotonically for anti-IgG antibody concentrations higher than 1 nM. AFM images reveal hardly any change of lateral nanostructure due to blocking but response to antibody solutions, based on both the mean size (from autocorrelation) and dominant spacing (from Fourier analysis) of surface features, similar to that given by ARXPS. AFM height histograms provided information about the vertical nanostructure and the parameters of height distribution (average height, spread – roughness and skewness) were distinctly influenced by coating, blocking and immunoreaction. Average protein layer thickness values determined based on protein structure (molecular weight, dimensions) and surface coverage provided from ARXPS were in accord with average height of protein layer determined from AFM. TOF-SIMS analysis indicated that BSA blocks free surface sites and in addition replaces some already adsorbed IgGs.

There are several techniques like time of flight secondary ion mass spectrometry (ToF SIMS) that require a special protocol for preparation of biological samples, in particular, those containing single cells due to high vacuum conditions that must be kept during the experiment. Frequently, preparation methodology involves liquid nitrogen freezing what is not always convenient. In our studies, we propose and validate a protocol for preparation of single cells. It consists of four steps: (i) paraformaldehyde fixation, (ii) salt removal, (iii) dehydrating, and (iv) sample drying under ambient conditions. The protocol was applied to samples with single melanoma cells i.e. WM115 and WM266-4 characterized by similar morphology. The surface and internal structures of cells were monitored using atomic force, scanning electron and fluorescent microscopes, used to follow any potential protocol-induced alterations. To validate the proposed methodology for sample preparation, ToF SIMS experiments were carried out using C 60 + cluster ion beam. The applied principal component analysis (PCA) revealed that chemical changes on cell surface of melanoma cells were large enough to differentiate between primary and secondary tumor sites. Subject category : Mass spectrometry.

Many of bioelectronic and biosensor applications are based on poly(3-alkylthiophenes), conducting and solution-processable polymers. The most facile approach for the fabrication of such devices relies on biofunctionalization of P3AT surfaces with antibodies through adsorption. The success of this approach depends critically on antibody orientation that affects its biorecognition. As demonstrated here both these features are controlled by the surface structure of spin-cast P3ATs. In particular, a multi-technique and multivariate study that involved Atomic Force Microscopy, Grazing Incidence X-ray Diffraction, Angle-Resolved X-ray Photoelectron Spectroscopy, Enzyme-Linked ImmunoSorbent Assay, and Time-of-Flight Secondary Ion Mass Spectrometry combined with Principal Component Analysis is conducted in order to deduce the crystalline texture of three P3AT polymers as well as its effect on orientation of adsorbed rabbit immunoglobulin (IgG) molecules. An edge-on crystalline texture is concluded for regioregular poly(3-butylthiophene) (RP3BT) and poly(3-hexylthiophene) (RP3HT), while amorphous morphology is inferred for poly(3-butylthiophene) (P3BT). In addition, end-on and head-on orientations similar for all P3ATs were concluded, based on the amount of adsorbed rabbit IgG molecules. Examination of amino acids characteristic for F(ab')2 and Fc fragments, and dominant in the external regions of adsorbed immunoglobulin molecules, points to end-on IgG alignment on RP3BT and RP3HT, but not on P3BT. Moreover, the binding of an anti-rabbit IgG antibody on the absorbed rabbit IgG is higher (up to 71%) when the biorecognition reactions are performed on regioregular rather than regiorandom P3AT surfaces. In particular, the highest biorecognition efficiency and IgG orientational order is observed for the RP3BT surfaces with the more developed crystallinity.

Self-organization of TiO 2 nanotubes was studied by means of titanium anodizing in electrolytes containing 1, 2 and 3 oxyethylene units in the organic chain of solvent molecule, named mono-, di-, and tri-ethylene glycols. A fundamentally different nanostructures were formed in mono- and di-electrolytes in view of their self-organization; close pack nanotubes are formed in mono-electrolyte, whereas nanotubes with large spaceing in-between are formed in di-electrolyte. The analysis of the tube bottoms and dimples formed in substrate shows formation of conical-type (alumina like) and frustum-type dimples in mono- and di-electrolytes, respectively. We discuss on the formation of frustum-type dimples with the size corresponding to the space in-between the nanotubes and link their formation to the mechanism of nanostructure growth.

In this work, the authors examine chemical stability of polymers under x-ray photoemission spectroscopy (XPS) depth profiling coupled with argon gas cluster ion sputtering. The depth profiles measured for polystyrene, poly(3-dodecylthiophene), and poly(methyl methacrylate) thin films do not reveal changes in the XPS spectra due to cluster bombardment. Nevertheless, x-ray irradiation influences the shape of the sputter craters. The observed features are attributed to cross-linking or chain scission occurring in the polymers.

The methods of preparation and characterization of core-shell poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) particles arranged in colloidal crystals are described. The particles were prepared via emulsifier free emulsion copolymerization of styrene and α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer in aqueous medium, initiated by potassium persulfate. The individual polymerizations differed in a way of addition of macromonomer to the polymerization mixture. The particles assemblies were characterized by atomic force microscopy, Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS). In-depth distribution of chemical states was determined by XPS combined with argon gas cluster ion sputtering (Ar-GCIB). The morphology of microspheres assemblies reflected the composition of the entire particles. It was found that the method of macromonomer addition to the polymerization mixture affects the particles size, surface and overall morphology. The XPS profiles revealed the chemical composition of the particles arranged in multilayers. It was found that distribution of polyglycidol segments at the particles interfacial layer depends on the time and way of addition of macromonomer. The thickest outer layer composed from polystyrene-polyglycidol segments was obtained for particles when macromonomer was added at the beginning of polymerization.

Near-field scanning optical microscopy is a technique providing images of structures with spatial resolution better than $\lambda/2$, which is undetectable in far-field where the Abbe law of limiting resolution is critical. In parallel to the optical imaging, topography maps are also acquired. Near-field scanning optical microscopy measurements can be performed both in air and liquid environments. The later makes the technique very useful for biomaterials analysis offering information that could not be obtained with other methods. Our work presents the results of recent studies on application of near-field scanning optical microscopy to imaging of cells in air as well as in physiological buffers. Differences in cell's topography and morphology have been noticed between two cell lines from human bladder non-malignant (HCV29) and malignant (T24) cancers. Presented results are part of the research that characterizes physiological changes of cells depending on stage of cancer.

In the present work morphological structures were examined which are formed spontaneously during the spin-casting of polymer blends. Mixtures of polyaniline (PANI) (doped with camphorsulfonic acid, CSA) or its oligomeric counterpart (N,N′-diphenyl-p-phenylenediimine, DPI) and a conventional polymer (polystyrene, PS or poly(methyl methacrylate), PMMA) were studied. The samples were manufactured in controlled humidity conditions (relative humidity, RH = 10%, 60% or 95%). In case of PANI(CSA)/PS (or PMMA) blends, hierarchic structures arise. They are built of large (>10 μm) PS-rich (or PMMA-rich) dendrites and sub-micron PANI-rich pillars in the pores of PS (PMMA) host. In analogous PS/DPI films, DPI dendrites embedded in the PS film are observed. This microstructure formation route, based on solution blend processing, is an alternative to chemical synthesis of fibres and columns. Film structures were determined with microscopic (optical, Atomic Force Microscopy) and spectroscopic techniques (dynamic Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy). Structure formation models are presented. Diffusion-Limited Aggregation is postulated for solution droplets agglomerating as PS-rich fractals (with low attachment probability P ) and for crystallizing DPI dendrites (with higher P value and hence larger and less compact fractals, as observed).

The origin and formation of the dipole moment at the interface of metal electrode and thin organic film is crucial for the fabrication of high‐performance organic electronic devices. In this work, model polymer multilayer systems are studied in which interfaces are modified heterogeneously with thiol‐based self‐assembled monolayers (SAM). Due to the presence of polar terminal group (‐COOH) in SAM and polar pendant groups (‐COOH, ‐C(O)OCH_{3}) within studied polymers, it is pointed out that the resultant interface energetics differ from the expected ones as one would expect from the chemical character of the self‐assembled molecules used to tune junction properties. This is discussed in terms of inter‐association and depolarization effects between polymer and thiol modified substrate. The presented model systems may serve as an interaction reference for SAMs and semiconducting polymers containing similar moieties, utilized for the fabrication of organic electronic devices.

Spin casting polymer blends of conjugated and dielectric macromolecules onto chemically patterned metal and oxidized silicon surfaces might provide a simple method to fabricate polymer-based circuitries that can be integrated with conventional electronics. Such solution-processing of the blend components offers simultaneous deposition and pattern-directed alignment of the phase separated polymer domains. The alignment is driven by self-organization guided by preferential surface segregation. Here we demonstrate that the laterally arranged domain structures in spin cast films of the conjugated poly(3-alkylthiophenes) (P3ATs): P3BT, P3DDT and regioregular R-P3HT, blended with dielectric polystyrene (PS), can be ordered by three different surface templates. The templates are formed by a patterned self-assembled monolayer (SAM), micro-contact printed on the surface of interest, i.e. hexadecanethiols on gold (for alignment of P3DDT/PS blend) and octadecyltrichlorosilanes on oxidized silicon (for R-P3HT/PS). Additionally gold lines are micro-patterned on SiO2 with photo-lithography (for P3BT/PS mixture). The forces driving pattern-directed self-organization of the polymers are discussed based on complementary studies of preferential surface segregation, observed for blend films spin cast on homogeneous surfaces that correspond to the different regions of the surface templates.

Jaczewska, J., Budkowski, A., Bernasik, A., Moons, E., Rysz, J.,Polymer vs. Solvent Diagram of Film Structures Formed in Spin-Cast Poly(3-alkylthiophene) Blends, Macromolecules 41, 13 (2008), p. 48 ...

We investigate effects of two spin-coating parameters, relative humidity (5%or = RHor = 80%) in ambient atmosphere and water content (3 wt %or = f(H2O)or = 20 wt %) in solution (rich in tetrahydrofuran), on the structure of breath figures (BF) formed in spin-cast films of polar poly(methyl methacrylate) (PMMA) and PMMA mixed with nonpolar polystyrene (PS). Film morphologies, examined with atomic and lateral force microscopy, are analyzed with integral geometry analysis to yield morphological BF measures. In PMMA, water added to solution has much stronger impact than that from moisture on formed BFs, which could be ordered (with conformational entropy S approximately 0.9-1.0). In PMMA/PS, BFs decorate exclusively polar PMMA domains, resulting in morphologies with two length scales (sub-micrometer BFs and domains10 microm). This suggests a novel strategy for herarchic structure formation in multicomponent polymer films. In PS/PMMA, BFs are better developed than in pure PMMA spin-coated in identical conditions. These observations show that the air boundary layer facing the spin-cast polymer film (region) is more important than the ambient atmosphere.

The early stages of phase evolution, not available for nanometer polymer blend films spin-cast from solutions of incompatible mixtures, have been examined for films prepared from nanoparticles of deuterated polystyrene/ poly(methyl methacrylate) blends (1:1 mass fraction of dPS/PMMA) with PS-PMMA diblock copolymer additives. The initial phase arrangement, confined to the size of nanoparticles, has provided the homogeneity of the initial film composition. The early stages of structure formation, promoted by annealing and traced with atomic and lateral force microscopy (AFM, LFM) as well as secondary ion mass spectroscopy (SIMS), resulted in bilayers, observed commonly for as-prepared solvent-cast blends. The initiated capillary instability of the upper dPS-rich layer depended on copolymer additives, which enhanced the lateral structures pinning the dewetting process.

Two blends (1:1 and 5:3 w:w) of poly(2-vinylpyridine) (PVP) and partly brominated polystyrene were spin-cast (with constant inherent domain scale 2R = 4.2 ± 0.5 μm) onto a gold substrate which had been microcontact printed with stripes of hexadecanethiol SAM. Two chemical patterns on the substrate were used, one with symmetrical stripes (4 μm Au/4 μm hexadecane SAM) and the other with narrow gold stripes and wider SAM stripes (3 μm/5 μm). The resulting film morphologies were mapped with atomic force microscopy. Secondary ion mass spectrometry shows that raised regions on the film surface correspond to PVP-rich domains, and the surface polymer composition extends all the way down to the substrate. Fourier analysis reveals structural modes (λ/n) smaller than the pattern periodicity λ = 8 μm. PVP preferentially adsorbs to the gold regions of the pattern. For the asymmetric pattern, which has a relatively small Au area interacting with the PVP, the fundamental mode (n = 1) is extinguished and higher-order sub...

A deep understanding of the interaction between cancerous cells and surfaces is particularly important for the design of lab-on-chip devices involving the use of polydimethylsiloxane (PDMS). In our studies, the effect of PDMS substrate stiffness on mechanical properties of cancerous cells was investigated in conditions where the PDMS substrate is not covered with any of extracellular matrix proteins. Two human prostate cancer (Du145 and PC-3) and two melanoma (WM115 and WM266-4) cell lines were cultured on two groups of PDMS substrates that were characterized by distinct stiffness, i.e. 0.75 ± 0.06 MPa and 2.92 ± 0.12 MPa. The results showed the strong effect on cellular behavior and morphology. The detailed analysis of chemical and physical properties of substrates revealed that cellular behavior occurs only due to substrate elasticity.

Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) mass spectra measurements combined with an appropriate sample preparation protocol are the powerful tools to obtain unique information about the chemical composition of biological materials. In our studies, two questions were addressed, i.e., whether it is possible to develop a fixative-based sample preparation protocol and whether it allows one to distinguish between cells originating from various stages of cancer progression. Therefore, four human bladder cancer cell lines (with distinct malignancy degree) have been investigated. A chemical fixation protocol has been used for TOF-SIMS measurements, and mass spectra were obtained using a Bi_{3}+ primary ion beam. The principal component analysis (PCA) has been applied to analyze the whole range of mass spectra (without preselection of any particular masses) using two approaches of data preprocessing, namely, mean centering and autoscaling. The PC3 versus PC2 plot has showed significant differences between nonmalignant cancer cells and the cancerous ones for both of preprocessing approaches. The analysis of mass spectra of human bladder cells allows one to find a list of mass peaks with intensities significantly larger in cancerous bladder cells compared to nonmalignant cell cancer of the ureter (HCV29 cells). These findings show that TOF-SIMS in combination with PCA can be used to identify reference, human bladder cells from cancerous ones.

The distribution of electron donor and acceptor in the active layer is known to strongly influence the electrical performance of polymer solar cells for most of the high performance polymer:fullerene systems. The formulation of the solution from which the active layer is spincoated plays an important role in the quest for morphology control. We have studied how the choice of solvent and the use of small amounts of a low vapour pressure additive in the coating solution influence the film morphology and the solar cell performance for blends of poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) and [6,6]-phenyl C71-butyric acid methyl ester (PC70BM). We have investigated the lateral morphology using atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM), the vertical morphology using dynamic secondary ion mass spectrometry (d-SIMS) and variable-angle spectroscopic ellipsometry (VASE), and the surface composition using near-edge X-ray absorption fine structure (NEXAFS). The lateral phase-separated domains observed in films spincoated from single solvents, increase in size with increasing solvent vapour pressure and decreasing PC70BM solubility, but are not observed when 1-chloronaphthalene (CN) is added. A strongly TQ1-enriched surface layer is formed in all TQ1:PC70BM blend films and rationalized by surface energy differences. The photocurrent and power conversion efficiency strongly increased upon the addition of CN, while the leakage current decreased by one to two orders of magnitude. The higher photocurrent correlates with the finer lateral structure and stronger TQ1-enrichment at the interface with the electron-collecting electrode. This indicates that the charge transport and collection are not hindered by this polymer-enriched surface layer. Neither the open-circuit voltage nor the series resistance of the devices are sensitive to the differences in morphology. © 2015 The Royal Society of Chemistry., E.M. acknowledges funding from the Swedish Research Council (Project 2010-4155) and the G¨oran Gustafsson Foundation for Research in Natural Sciences and Medicine. M.C.-Q. thanks the Spanish Ministerio de Econom´ıa y Competitividad for nancial support through project PHOTOCOMB (MAT2012-37776). A.O. acknowledges the R¨ontgen–°Angstr¨om– Cluster for nancial support. E.W. acknowledges the Swedish Research Council for nancial support. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Selenolate is considered as an alternative to thiolate to serve as a headgroup mediating the formation of self-assembled monolayers (SAMs) on coinage metal substrates. There are, however, ongoing vivid discussions regarding the advantages and disadvantages of these anchor groups, regarding, in particular, the energetics of the headgroup-substrate interface and their efficiency in terms of charge transport/transfer. Here we introduce a well-defined model system of 6-cyanonaphthalene-2-thiolate and -selenolate SAMs on Au(111) to resolve these controversies. The exact structural arrangements in both types of SAMs are somewhat different, suggesting a better SAM-building ability in the case of selenolates. At the same time, both types of SAMs have similar packing densities and molecular orientations. This permitted reliable competitive exchange and ion-beam-induced desorption experiments which provided unequivocal evidence for a stronger bonding of selenolates to the substrate as compared to the thiolates. Regardless of this difference, the dynamic charge transfer properties of the thiolate- and selenolate-based adsorbates were found to be nearly identical, as determined by the core-hole-clock approach, which is explained by a redistribution of electron density along the molecular framework, compensating the difference in the substrate-headgroup bond strength.

While it is a common concept in chemistry that strengthening of one bond results in weakening of the adjacent ones, no results have been published on if and how this effect protrudes further into the molecular backbone. By binding molecules to a surface in the form of a self-assembled monolayer, the strength of a primary bond can be selectively altered. Herein, we report that by using secondary-ion mass spectrometry, we are able to detect for the first time positional oscillations in the stability of consecutive bonds along the adsorbed molecule, with the amplitudes diminishing with increasing distance from the molecule-metal interface. To explain these observations, we have performed molecular dynamics simulations and DFT calculations. These show that the oscillation effects in chemical-bond stability have a very general nature and break the translational symmetry in molecules. Self-assembled monolayers (SAMs) (1) are a nanotechnolog- ical system, in which molecules are chemically bonded to a substrate in an ordered and oriented fashion. The influence of the strength of the molecule-substrate bond on the structure and stability of SAMs is still poorly understood even for the most simple system of methanethiol on Au- (111). (2) As it is known from other fields of chemistry, the formation of a strong bond (in this case to the surface) should lead to a weakening of the adjacent bonds within the molecules. Thus, it would be interesting from a very basic point of view as well as technologically relevant to determine these influences. We decided to take a new approach by exploiting static secondary-ion mass spectrometry (SSIMS) in combination with the molecular dynamics (MD) simulation of such experiments and density functional theory (DFT) calcula- tions. As model SAMs we have selected two homologous series of the general form CH3-(C6H4)2-(CH2)n-S(Se)/Au- (111), (BPnS(Se), n = 1-6), for which either sulfur atoms or selenium atoms (BPnSe) act as a binding groups to the Au(111) substrate. Previous microscopic (3-5) and spectroscop- ic (6-9) studies demonstrated that the BPnS(Se)/Au(111) pack- ing structure, unlike other SAMs, remains virtually the same for the S and Se analogues within both series. This means that intermolecular interactions in these SAMs are identical when comparing the respective members of both families and thus the only source of difference in stability between them is the binding atom (S vs. Se). Analysis of such SAMs gives a direct way to trace molecule-substrate interface energetics. Positive and negative SSIMS mass spectra are presented in Figure S1 in the Supporting Information. The most

Two off-critical blends of poly(2-vinylpyridine) and polystyrene, 2:3 and 3:2 (w:w) PVP:PS, were spin-cast (with varied domain scale R) onto periodically (λ = 4 μm) patterned substrate. The pattern consisted of two alternating symmetric stripes: Au attracting PVP and neutral self-assembled monolayer. The resulting droplet-type morphologies were recorded with Scanning Force Microscopy and examined with integral geometry approach. PVP-rich islands of the 2:3 PVP:PS films form, for a wide R/λ range, strongly anisotropic morphologies. They show up, for R/λ ∼ 0.5, a weak λ/2-substructure of smaller PVP droplets in addition to the domains periodic with λ. The 3:2 blend exhibits morphologies with dominant λ-structure of PVP ribbons, which encircle PS droplets. For R/λ ∼ 0.5, smaller PS domains are also present but no λ/2-substructure is formed. The |χE|-values of droplet surface density are reduced, as compared to homogeneous substrate, for the 3:2 blend (with |χE| → 0 for R ∼ λ). This effect is absent for the 2:3 mixture.

Blends of the low-bandgap polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4',7'-di-2-thienyl- 2',1',3'-benzothiadiazole)] (APFO-3) and the fullerene deriv. [6,6]-phenyl-C61-butyric acid Me ester (PCBM) were spin-coated from chloroform soln. into thin films, which were examd. with dynamic secondary ion mass spectrometry. For blends with high PCBM content, the depth profiles show compn. waves that were caused by surface-directed phase sepn. during spin-coating. The formation of such multilayer structures by spontaneous self-stratification probably has implications for optimization strategies for the performance of org. solar cells. [on SciFinder (R)]

Blends of poly(2-vinylpyridine), polystyrene, and poly(methyl methacrylate) of four different compositions (2:3:0, 3:2:0, 1:1:0, and 2:2:1 w:w:w) were spin-cast onto periodically (λ = 4 μm) patterned substrate (with two alternating stripes: Au attracting PVP and neutral self-assembled monolayer), and resulting film morphologies (with inherent domain scale 0.2 λ ≤ R < 1.8 λ) were recorded with scanning force microscopy and examined with Fourier transform analysis and the integral geometry approach. The morphologies depend on not only spatial (R/λ) but also compositional commensuration between blends and symmetric pattern: λ/2-substructures are present, in addition to λ-structures, for isolated (2:3:0) but not for continuous (3:2:0) PVP domains. This explains also the data for 1:1:0 blends which present a transition from isolated to continuous PVP domains (for larger R values). In turn, interfacial compatibilizer (PMMA in 2:2:1) results in the well-ordered λ/2-substructures for both morphology types.

An extension of the integral geometry approach, proposed to characterize pattern replication, was used to compare quantitatively the surface pattern of spin-cast polymer blend films with that replicated in their substrate by ion milling. The original and replicated patterns, recorded with atomic force microscopy (AFM) and analyzed in terms of the Minkowski measures plotted as a function of height, were characterized by the vertical extent and lateral morphological measures. Good, moderate, and far from ideal replication was discussed for various types (island-, hole-dominated, and bicontinuous, respectively) of the original pattern, formed by binary (deuterated) polystyrene mixtures with polyisoprene and poly(n-butyl methacrylate).

Surface directed phase separation in thin polymer blend film has been studied with Monte Carlo simulations using a simple model based on reptation method. Time evolution of phase structure was characterized quantitatively by morphological measures (the Minkowski functionals) in addition to the inspection of concentration versus depth profiles. It was shown that the dynamical scaling hypothesis holds for the Minkowski functionals describing morphologies at the early stages of phase separation in thin films. Two time regimes with different scaling exponents (0.25, 0.33) were found for the growth of the characteristic length scale in the system corresponding to various transport mechanisms (diffusion along- and normally to the interface). Fast decrease in the morphological measures observed at the end of phase separation was attributed to the confinement of the thin film.

Distribution of polyaniline doped by camphorsulfonic acid, blended with polystyrene of different molecular weight and spin-cast from chloroform into (50–400 nm thick) films, was examined using secondary ion mass spectrometry (SIMS). Strong polyaniline segregation to the Au substrate was observed to be accompanied by depletion region or, for thicker films, by concentration oscillations. Segregation and substrate-directed phase separation, effective during solvent removal, form lamellar film structures.

A chemical pattern on a substrate is transposed into thin films of a ternary polymer blend during spin-casting from a common solvent. One of the blend components intercalates at interfaces between the other two phases to reduce their interfacial energy. As a result, an extensive substructure is formed, in addition to domains with pattern periodicity lambda. Morphologies with well-ordered lateral domains are created not only when the inherent scale of the phase domains R is comparable to lambda (as observed previously) but also for R similar to lambda/2, extending pattern transposition to smaller length scales.

Sectional views of thin films of symmetric polystyrene/polyisoprene (PS/PI) blends spin- cast from toluene (C6H5CH3) onto CH3- and COOH-terminated self-assembled monolayers (CH3-SAM and COOH-SAM) show concave- (sharp-edged) and convex-shaped (round) protrusions, respectively, while other morphology features are identical. A 3-dimensional phase domain arrangement was determined with spectroscopic techniques (profiling and mapping mode of dynamic secondary ion mass spectrometry, dSIMS, and X-ray photoelectron spectroscopy). Surface topography was examined with atomic force microscopy and monitored, during the dSIMS analysis, with secondary electrons. In addition, solvent evaporation from PS, PI, and PS/PI layers cast on CH3-SAM and COOH-SAM was determined. The collected data were used to put forward a model of morphology formation and to elucidate the role of evaporation speed dependent on substrate chemistry in this process, demonstrated here for the first time.

Topography and composition images of model thin films of deuterated polystyrene (dPS) and polyisoprene with different blend compositions were analyzed with an extension of integral-geometry approach. Surface patterns, formed in the course of spin-casting from toluene onto self-assembled monolayers (SAM), were recorded with scanning force microscopy. Their relation with lateral phase domain structures was demonstrated by dynamic secondary ion mass spectrometry, yielding maps of dPS distribution. Morphological measures, which cannot be provided by Fourier transform analysis (FTA), characterize individual images, compositional series of the surface patterns and individual features of the patterns. Different morphologies (nucleation- and spinodal-type and hole- and island-dominated ones) are consistently characterized by the Minkowski measures and related parameters. For instance, the latter can measure circular character of the individual features and estimate dominant lateral length (determined rigorously w...

Poly( N -methacryloyl- l -leucine) (PNML) coatings were successfully fabricated via polymerization from peroxide initiator grafted to premodified glass substrate. Chemical composition and thickness of PNML coatings were determined using time of flight-secondary ion mass spectrometry (TOF- SIMS) and ellipsometry, respectively. PNML coatings exhibit thermal response of the wettability, between 4 and 28 °C, which indicates a transition between hydrated loose coils and hydrophobic collapsed chains. Morphology of the PNML coating was observed with the AFM, transforming with increasing temperature from initially relatively smooth surface to rough and more structured surface. Protein adsorption observed by fluorescence microscopy for model proteins (bovine serum albumin and lentil lectin labeled with fluorescein isothiocyanate) at transition from 5 to 25 °C, showed high affinity of PNML coating to proteins at all investigated temperatures and pH. Thus, PNML coating have significant potential for medical and biotechnological applications as protein capture agents or functional replacements of antibodies (“plastic antibodies”). The high proliferation growth of the human embryonic kidney cell (HEK 293) onto PNML coating was demonstrated, indicating its excellent cytocompatibility.

Thin polymer films with lateral structures are expected to play an important role in future applications (e.g. plastic-based electronic devices). Such structures could be formed when blend films are spun-cast onto substrates patterned with self-assembled monolayers (SAM). The spin-coating process results in composition variations accompanied by surface undulations. We have studied both phenomena for PVP/dPS and PVP/PBrS blends, composed of poly(vinylpyridine) (PVP) and deuterated (dPS)- or brominated (PBrS)-polystyrene. SAM stripes of HS(CH 2 ) 15 CH 3 on Au substrate (‘bare’ or covered with HS(CH 2 ) 15 COOH) were used as the pattern with periodicity of 4 μm. Transfer of the pattern from the substrate to the film interior and to the film surface was examined with secondary ion mass spectroscopy (SIMS) and atomic force microscopy (AFM) combined with selective dissolution of blend components. Characteristic size D of the phase domains corresponding to given spin-casting conditions was determined for the blends cast on homogeneous SAM substrate. Fourier transform analysis (FTA) of topographic (AFM) and compositional (SIMS) maps was performed. FTA confirms that the pattern-directed composition variations coincide with the surface undulations. It reveals also that most effective pattern transfer is achieved for the size D commensurate with the pattern periodicity for the carefully adjusted polymer–substrate interactions.

We describe the technique of dynamic secondary ion mass spectrometry developed to determine three-dimensional phase domain structures of films of polymer blends. The polymers are composed of light elements or are labeled with deuterium or heavy elements. The applicability of this method to various polymer blends forming thin and ultrathin films with flat and undulated air/film interface is discussed.

Thin "lms, formed by polymer blends spun-cast from a blend/solvent solution onto a rigid substrate, are used in many practical applications (e.g. photoresist layers, dielectric coatings). Film preparation process is often accompanied by phase decomposition (PD) during the rapid evaporation of the solvent. PD is re#ected in undulations formed on an air/"lm interface. We have studied the topography of surface undulations and the phase domain morphology in thin "lm blends of polystyrene (PS) and polyisoprene (PI) using atomic force microscopy combined with selective dissolution of blend components. Gold covered with self-assembled monolayers [HS(CH ) COOH] [HS(CH ) CH ] (SAM ) was used as a substrate. For "lms of PS and PI (50% by mass) cast from toluene, the PS-rich domains protrude high above the PI-rich matrix forming concave or convex islands for hydrophobic (SAM )- or hydrophilic(SAM )-support, respectively. Di!erent substrates (e.g. SAM and Si with a native oxide layer), solvents (CCl , chloroform) and PS mass fractions were used to evaluate the extent of this novel e!ect. 2001 Elsevier Science Ltd. All rights reserved.

External surfaces can significantly alter the phase decomposition (PD) of polymer mixtures in thin films. The surface mode of PD orders two coexisting phases in organised structures with laminated domain morphology. Such structures are employed in new polymer-based technologies of photoelectronic devices or microelectronic circuits. We studied the surface mode of PD in thin films composed of various binary mixtures of polystyrene with its deuterated- and partially brominated- counterpart. We have examined how PD is influenced by: (a) surface active diblock copolymers admixed to decomposing blends, (b) substrate surface modification, and (c) finite film thickness. Thin films were studied by nuclear reaction analysis (NRA) and secondary ion mass spectroscopy (SIMS). The results provided composition profiles as a function of depth in the film with a nanometer precision, comparable with the polymer chain dimensions. Lateral morphology was investigated by means of the atomic force microscope and optical microscope. Various laminated structures composed of 2-, 3-, or 4- layers or column-like structures self-stratified from initially homogenous films were observed.

According to a common viewpoint the surface of the binary polymer mixture A/B could be enriched only in one component, say A, regardless of the value of its bulk volume fraction φ bulk . From recent theoretical analyses and Monte Carlo simulations one can expect however that some mixtures can exhibit surface segregation in the minority blend component, i.e. enrichment in the component A for φ bulk φ bulk >50%. Using composition-depth profiling techniques, we have observed both types of the segregation with only one- or both-blend component(s) preferred at the surface. These results were obtained for model mixtures composed of partly deuterated (dx) and protonated (hx) random olefinic copolymers of the structure –[C 4 H 8 ] 1- x [C 2 H 3 (C 2 H 5 )] x –. A simple mean-field model is presented to explain both situations.

We have examined the effect of deuterium labeling on surface interactions in mixtures of random olefinic copolymers [C 4 H 8 ] 1 x [C 2 H 3 (C 2 H 5 )] x . Based on surface segregation data we have determined a surface energy difference X s between pure blend constituents. In each binary mixture components have different fractions x 1 , x 2 of the group C 2 H 3 (C 2 H 5 ), and one component is labeled by deuterium (dx) while the other is hydrogenous (hx). The mixtures are grouped in four pairs of structurally identical blends with swapped labeled constituent (dx 1 /hx 2 , hx 1 /dx 2 ). For each pair the surface energy parameter x s increases when the component with higher fraction x is deuterated, i.e., X s (dx 1 /hx 2 ) > X s (hx 1 /dx 2 ) for x 1 > x 2 . A similar pattern has been found previously for the bulk interaction parameter X. This is explained by the solubility parameter formalism aided by the lattice theory relating the surface excess to missing-neighbor effect. X s has also an additional contribution, insensitive to deuterium swapping effect, and related to entropically driven surface enrichment in a more stiff blend component with a lower fraction x. Both enthalpic and entropic contributions to X s seem to depend on the extent of chemical mismatch between blend components.

We have measured the surface segregation towards the vacuum in films of a binary mixture of deuterated E48EE52 (d52)—and hydrogenous E38EE62 (h66)—random olefinic copolymers. Here E and EE are the linear ethylene and branched ethyl ethylene groups (C4H8) and [C2H3(C2H5)], respectively. The d52 copolymer is enriched at the surface when d52 is the minority component in the blend. On the contrary, the surface is depleted in the d52 chains, when they constitute a majority of the mixture. We have determined two branches of the segregation isotherm corresponding to the enrichment and the depletion. A mean-field Cahn model describes consistently these two isotherm branches. The observed enrichment-depletion duality modifies a common viewpoint on surface segregation.

We have studied the surface-induced spinodal decomposition in thin films of deuterated and protonated polystyrene, using 3He nuclear-reaction analysis and dynamic secondary-ion mass spectroscopy. We found that the amplitude of this process may be modified by a polyisoprene-polystyrene diblock copolymer, which segregates predominantly to the surface when admixed to the isotopic polystyrene blend. This is due to the reduced surface attraction of deuterated polystyrene for the increased surface coverage by diblocks. Finally, the surface directed mode of the spinodal decomposition is observed to be extinct for the surface completely covered by copolymers.

Device performance in organic electronics depends on electronic properties of buried interfaces between thin (

Poly(oligo(ethylene glycol)ethyl ether methacrylate (POEGMA246) coatings were successfully fabricated using novel approach via polymerization from oligoperoxide grafted to premodified glass substrate. Wettability, content and composition of coatings fabricated with different polymerization times were determined using contact angle measurements, ellipsometry and Time of Flight-Secondary Ion Mass Spectrometry (TOF-SIMS). Thermo- and pH-responsive properties of POEGMA246 coatings were found to depend significantly on concentration of the grafted POEGMA246. Coatings fabricated with polymerization time 30 h exhibit not only temperature- but also pH-dependence of wettability. Thermal response of wettability, measured between 20 and 32 °C, was prominent at pH 9 and 7 and diminished or was absent at pH 5 and 3, indicating a transition between hydrated loose coils and hydrophobic collapsed chains, blocked at low pH. Protein adsorption, observed by fluorescence microscopy and analyzed semi-quantitatively using integral geometry approach, decreased dramatically for model protein (lentil lectin labeled with fluorescein isothiocyanate) at transition from pH 5 to pH 9, showing only very weak thermal-dependence. Strong protein adsorption response to pH and very weak one to temperature was confirmed by TOF-SIMS and Principal Component Analysis.

Organo-silanes provide a suitable interface between the silicon-based transducers of various biosensing devices and the sensing proteins, immobilized through physical adsorption, as for (3-aminopropyl)triethoxysilane (APTES), or covalent binding, e.g. via protein amine groups to (3-glycidoxypropyl)trimethoxysilane (GOPS) modified surface. Immobilization of rabbit gamma globulins (RgG) to silicon nitride surfaces, modified either with APTES or GOPS, was examined as a function of incubation time using atomic force microscopy (AFM), angle-resolved X-ray photoelectron spectroscopy (ARXPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). Multivariate technique of principal component analysis was applied to ToF-SIMS spectra in order to enhance sensitivity of immobilized RgG detection. Principal component regression shows a linear relationship with surface density determined rigorously from ARXPS following an organic bilayer approach, allowing for protein coverage quantification by ToF-SIMS. Taking it overall the surface immobilized amount of RgG is higher and develops faster on the surfaces silanized with APTES rather than with GOPS. Similar, although less distinct, difference is observed between the two surface types concerning the temporal evolution of average AFM height. The average height of protein overlayer correlates well with ARXPS and ToF-SIMS data expressed in terms of protein surface density. However, determined linear regression coefficients are distinctively higher for the surfaces modified with epoxy- rather than amino-silane, suggesting different surface density and conformation of the proteins immobilized through to covalent binding and physical adsorption.

Despite the advances in optical biosensors, the existing technological approaches still face two major challenges: the inherent inability of most sensors to integrate the optical sourc e in the transducer chip, and the need to specifically design the optical transducer per application. In this work, the development of a radical optoelectronic platform is demonstrated based on a monolithic optocoupler array fabricated by standard Si-technology and suitable for multi-analyte detection. The platform has been specifically designed biochemical sensing. In the all-silicon array of transducers, each optocoupler has its own excitation source, while the entire array share a common detector. The li ght emitting devices (LEDs) are silicon avalanche diodes biased beyond their breakdown voltage and emit in the VIS -NIR part of the spectrum. The LEDs are coupled to individually functionalized optical transducers that converge to a single detector for multiplexed operation. The integrated nature of the basic biosensor scheme and the ability to functionalize each transducer independently allows for the development of miniaturized optical transducers tailored towards multi -analyte tests. The monolithic arrays can be used for a plethora of bio/chemical interactions becoming thus a versatile analytical tool. The platform has been successfully applied in bioassays and binding in a real -time and label-free format and is currently being applied to ultra-sensitive food safety applications.

Poly(N-isopropylacrylamide) (PNIPAM) coatings attached to glass with novel approach involving polymerization from oligoperoxide grafted to surface with (3-aminopropyl)triethoxysilane exhibit not only temperature- but also pH-dependence of wettability and protein adsorption. Wettability and composition of coatings, fabricated with different polymerization times, were determined using contact angle measurements and Time Of Flight-Secondary Ion Mass Spectrometry (TOF-SIMS), respectively. Thermal response of wettability, measured between 20 and 40 $^{\circ}$C, was prominent at pH 9 and 7 and diminished or absent at pH 5 and 3. This indicates a transition between hydrated loose coils and hydrophobic collapsed chains that is blocked at low pH. Higher surface roughness and dramatically increased adsorption of model protein (lentil lectin labeled with fluorescein isothiocyanate) were observed with AFM and fluorescence microscopy to occur in hydrophobic phases (at pH 3, for pH varied at constant temperature of 22 $^{\circ}$C and at $\sim 33 ^{\circ}$C, for temperature varied at constant pH 9). Protein adsorption response to pH was confirmed by TOF-SIMS and Principal Component Analysis.

Versatility of solution-processing strategy based on the simultaneous rather than additive deposition of different functional molecules is discussed. It is shown that spin-cast polymer blends result in films with domains that could form elements with complementary functions of (i) solar cells, (ii) electronic circuitries, and (iii) test plates for protein micro-arrays: Alternating layers, rich in electron-donating polyfluorene and electron-accepting fullerene derivative, result in optimized solar power conversion. Surface patterns, made by soft lithography, align conductive paths of conjugated poly(3-alkylthiophene) in dielectric polystyrene. Proteins, preserving their biologically activity, are adsorbed to hydrophobic domains of polystyrene in hydrophilic matrix of poly(ethylene oxide). The authors report the research progress on structure formation in three polymer blend families, resulting in films with complementary elements for electronics and biotechnology. Blend film structures are determined with secondary ion mass spectrometry, atomic force microscopy, and fluorescence microscopy. In addition, the authors present recent results on (i) structure formation in fullerene derivative/poly(3-alkylthiophene) blends intended for solar cells, (ii) 3-dimensional SIMS imaging of conductive paths of poly(3-alkylthiophene) in dielectric polystyrene, (iii) test plates for multiprotein micro-arrays fabricated with blend films of hydrophobic polystyrene and thermoresponsive poly(N-isopropylacrylamide).

The fabrication of a power-free, reversible, color-indicator sensor of the relative humidity in the environment has numerous applications and is considered a challenging task. The device to be developed should be able of color changing according to the degree of humidity change and have a number of characteristics, i.e., reversibility, fast response, low cost, and, ideally, should be flexible. The proposed solution, based on a 1-D polymeric Photonic Crystal (PC) configuration on a microscope glass, can successfully fulfill all the above requirements.

We characterize an approach enabling protein patterning over broad polymer areas based on selective protein adsorption on surfaces of spin-cast amino-terminated polystyrene structured topographically with elastomer molds (capillary force lithography) and passivated locally against adsorption with poly(ethylene oxide)-silanes printed with flat elastomer stamps (inverted micro-contact printing). Atomic force microscopy reveals uniformity of $PS-NH_{2}$ films with stripes of grooves and elevations alternating with periodicity $4 < \lambda < 200 \mu m$. Film morphologies, prior and after selective adsorption of model protein, are mapped with optical and fluorescence microscopes, respectively. The examination with the Fourier analysis shows that elevated regions of polymer relief are replicated as dark or bright stripes on fluorescent micrographs for elevations forming plateaus ($>3 \mu m$) or narrow ridges, respectively. Reverse contrast in protein micro-patterns is induced by modified relief geometry, which affects surface flux of silanes from stamp to polymer surface both within and away from contact zones of micro-contact printing. In addition, protein substructures with a fraction $\lambda/n$ of relief periodicity are observed on surfaces with elevated ridges (n = 2) and plateaus (n = 2 and 4). This is due to the locally modified protein adsorption with silane concentration and surface topography, respectively.

Achieving control over the nanomorphology of blend films of the fullerene derivative [6,6]-phenyl C61-butyric acid methyl ester, PCBM, with light-absorbing conjugated polymers is an important challenge in the development of efficient solutionprocessed photovoltaics. Here, three new polyfluorene copolymers are presented, tailored for enhanced miscibility with the fullerene through the introduction of polymer segments with modified side chains, which enhance the polymer’s polar character. The composition of the spincoated polymer:PCBM films is analyzed with dynamic secondary ion mass spectrometry (dSIMS). The dSIMS depth profiles demonstrate compositional variations perpendicular to the surface plane, as a result of vertical phase separation, directed by the substrate. These variations propagate to a higher degree through the film for the polymers with a larger fraction of modified side chains. The surface composition of the films is studied by Near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Quantitative analysis of the NEXAFS spectra through a linear combination fit with the spectra of the pure components yields the surface composition. The resulting blend ratios reveal polymer-enrichment of the film surface for all three blends, which also becomes stronger as the polar character of the polymer increases. Comparison of the NEXAFS spectra collected with two different sampling depths shows that the vertical composition gradient builds up already in the first nanometers underneath the surface of the films. The results obtained with this new series of polymers shed light on the onset of formation of lamellar structures in thin polymer:PCBM films prepared from highly volatile solvents. Refereed/Peer-reviewed

An approach to determine structural features, such as surface fractional coverage F and thickness d of protein layers immobilized on silicon substrates coated with amino-organic films is presented. To demonstrate the proposed approach rabbit gamma globulins (RgG) are adsorbed from a 0.66 mu M solution onto SiO(2) and Si(3)N(4) modified with (3-aminopropyl)triethoxysilane (APTES). Atomic force microscopy data are analyzed by applying an integral geometry approach to yield average coverage values for silanized Si(3)N(4) and SiO(2) coated with RgG, F= 0.09 +/- 0.01 and 0.76 +/- 0.08, respectively. To determine the RgG thickness d from angle-resolved X-ray photoelectron spectroscopy (ARXPS), a model of amino-organic bilayer with non-homogeneous top lamellae is introduced. For an APTES layer thickness of 1.0 +/- 0.1 nm, calculated from independent ARXPS measurements, and for fractional surface RgG coverage determined from AFM analysis, this model yields d = 1.0 +/- 0.2 nm for the proteins on both silanized substrates. This value, confirmed by an evaluation (1.0 +/- 0.2 nm) from integral geometry analysis of AFM images, is lower than the RgG thickness expected for monomolecular film (similar to 4 nm). Structures visible in phase contrast AFM micrographs support the suggested sparse molecular packing in the studied RgG layers. XPS data, compared for bulk and adsorbed RgG, suggest preferential localization of oxygen- and nitrogen-containing carbon groups at silanized silicon substrates. These results demonstrate the potential of the developed AFM/ARXPS approach as a method for the evaluation of surface-protein coverage homogeneity and estimation of adsorbed proteins conformation on silane-modified silicon substrates used in bioanalytical applications. (c) 2010 Elsevier B.V. All rights reserved. Colloids and Surfaces B-Biointerfaces