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Purpose The purpose of this paper is to develop a meta-model of organizational change that allows to look at change from different angles. This meta-model starts from the idea that there are different discourses about organizational change, each having their own merits but also their own limitations. Bringing these discourses together into an integrated systems model allows the authors to capture the essence of organizational change a lot better. Design/methodology/approach This model is designed based on a literature review of organizational theories, systems theories related to theories of organizational change and specific theories about organizational change. Findings The literature review resulted in a systems model of organizational change that is better able to grasp the complexity of change than linear models. Originality/value This model goes beyond the usual change models from the normative discourse and provides a multidimensional view on organizational change.

In order to enable an oxide-free Cu-to-Cu bonding in a (dual) damascene process, 3-aminopropyltrimethoxysilane- and decanethiol-derived self-assembled monolayers are selectively deposited in a dielectric-Cu based metal-insulator-metal (MIM) capacitor used as a test vehicle, which represents a dual damascene architecture environment. A two-steps SAM coating sequence is investigated for this purpose. In a first step, a ''sacrificial'' SHSAM is deposited on the Cu areas at the bottom of the vias. In a second step, a ''barrier'' NH"2SAM is deposited on the dielectric areas in the field region and via's sidewalls. This deposition sequence followed by the selective thermal ablation of the ''sacrificial'' SAM vs. the ''barrier'' SAM, enable an oxide-free Cu-to-Cu connection at via's bottom. The differential in thermal stability between the amino and thiol SAMs has been studied by water contact angle and cyclic voltammetry. While the sacrificial SAM is selectively desorbed by thermal ablation already at ~200^oC, the barrier SAM on the dielectric sidewall and field regions withstands a thermal budget as high as ~350^oC. The substrate-selective SAMs depositions are revealed by XPS chemical characterization on the Cu and dielectric areas of the MIM structures supported by the SEM visualization of the Au nanoparticles that selectively decorate the NH"2 functionalities of the barrier SAM.

The H-bond complex formation between 1-methyluracil and glycine has been investigated by theoretical calculations and the most stable complex configurations have been identified by FT-IR spectroscopy in Ar matrices. The importance of this H-bonding system is huge since all DNA biological functions are dependent on the interactions with proteins. The theoretical optimizations have revealed six different closed H-bond complexes between 1-methyluracil and glycine. The obtained energies have demonstrated that the uracil C(4)═O site is a better H-acceptor site than the C(2)═O site. The stabilization energy of the most stable complex is -47.83 (MP2) or -54.14 kJ·mol(-1) (DFT). The DFT(B3LYP)/6-31G optimized geometries have been evaluated, and the obtained energies appeared to be in agreement with the results of the computational more expensive DFT(B3LYP)6-31++G** approach. In order to identify the 1:1 complexes in an argon matrix, a new dual miniature furnace has been developed which allows to sublimate both complex partners at their optimal temperature. The presence of three different glycine·1-methyluracil complexes has been demonstrated by analysis of the H-bond shifted modes. The H-bond parameters have been evaluated and previously obtained correlations for different H-bond complexes have been confirmed.

The conformational landscape of isoleucine was investigated by a theoretical DFT and MP2 study. This investigation has revealed new important conformations in comparison to a previous study. Five conformations have been predicted with an abundance larger than 5% at both levels of theory. Among these, three different types of amino acid backbone were present, each characterized by a typical intramolecular H-bond. Due to the H-bonding, the frequencies of the involved groups are strongly shifted, and these modes were probably observed with FT-IR spectroscopy in an Ar matrix. The experimental abundances could be estimated and were in good accordance with the MP2 stabilities, whereas the accordance with the DFT abundances was poor. In contrast to this, the correspondence of the DFT and the experimental frequencies was excellent, as demonstrated by the mean frequency deviation of only 4.7 cm(-1).

The conformational landscape of N -acetylalanine has been investigated by a theoretical and matrix-isolation FT-IR study. Optimizations of N -acetylalanine structures has been conducted at successive higher levels of theory HF/3-21G, DFT(B3LYP)/6-31++G** and MP2/6-31++G**. This resulted in three stable conformations. Among these, one conformation contains an intramolecular H-bond. The vibrational properties of these conformations were calculated and used to identify the conformations in a cryogenic argon matrix. The intensities of some bands assigned to a particular conformation were used to estimate the rotamerization constants K r12 and K r13 for the equilibria NAA1 NAA2 and NAA1 NAA3, respectively. The obtained experimental values were in agreement with the theoretical predictions.

Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of a polyfunctional heterocyclic base 3-methyl-4- pyrimidone molecule with a series of proton donors of different acidic strength, i.e. water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol, pentachlorophenol, picric acid and hydrogen chlordide. Computed H-bond interaction energies (ΔEc), internuclear and intermolecular distances r(O…H) and r(O…O), infrared frequency shifts Δv(C=O) and (Δv(OH) are proved to be reliable parameters for predicting the preferred interaction site of 3-methyl-4-pyrimidone. These computational data suggest that the O-H…O=C complex is preferred with water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol and pentachlorophenol. However, for H-bonding with stronger acids such as picric acid or hydrochloric acid, the computational data suggest that the H-bonding occurs at the N1 ring atom of 3-methyl-4-pyrimidone. In the O-H…O=C com- plex, where the H-bond at the carbonyl O-atom can be oriented “anti” (Ha) and “syn” (Hb) with respect to the N3 atom, the same computational data suggest a higher stability of the “anti-O” compared to the “syn-O” orientation.

Gentle manipulation of micrometer-sized dielectric objects with optical forces has found many applications in both life and physical sciences. To further extend optical trapping toward the true nanometer scale, we present an original approach combining self-induced back action (SIBA) trapping with the latest advances in nanoscale plasmon engineering. The designed resonant trap, formed by a rectangular plasmonic nanopore, is successfully tested on 22 nm polystyrene beads, showing both single- and double-bead trapping events. The mechanism responsible for the higher stability of the double-bead trapping is discussed, in light of the statistical analysis of the experimental data and numerical calculations. Furthermore, we propose a figure of merit that we use to quantify the achieved trapping efficiency and compare it to prior optical nanotweezers. Our approach may open new routes toward ultra-accurate immobilization and arrangement of nanoscale objects, such as biomolecules.

In this study a double-bead sandwich assay, employing magnetic nanoparticles and gold nanoparticles is proposed. The magnetic nanoparticles allow specific capturing of the analyte in biological samples, while the optical properties of the gold nanoparticles provide the signal transduction. We demonstrated that a major improvement in the assay sensitivity was obtained by selecting an optimal gold nanoparticle size (60 nm). A detection limit of 5-8 ng/mL, a sensitivity of 0.6-0.8 (pg/mL)(-1) and a dynamic range of 3 orders of magnitude were achieved without any further amplification using the detection of prostate specific antigen in serum as a model system. The proposed assay has the ability to be easily implemented within a microfluidic device for point-of-care applications whereby the readout can be executed by a fast and cheap optical measurement.

The hydrogen bonded complexes between N,N-diethylnicotinamide and proton donors such as phenol derivatives or hydrochlorid acid have been studied by infrared spectrometry. The thermodynamic parameters, the ΔνOH values and the shift of the νCO band to lower frequencies indicate that with phenol derivatives (pKa=10.2 -7.7 ), normal CO…HO hydrogen bonds are formed. The spectra show that the adduct with HCI is a proton transfer complex and that the protonation occurs at the nitrogen atom of the pyridine ring.

Raman spectra of several pyridine derivatives (substituent = CH3-, tC4H9-, Cl-, Br-, I-) complexed with bromine are studied in CH2Cl2 and in CH3CN. Marked changes in frequency, intensity and degree of depolarization of the Raman bands of pyridines are observed. These spectral perturbations seem to depend on the position of the substituent and are further discussed in terms of the charge transfer theory.

Raman spectra of Bu4NHSO4 dissolved in acetonitrile have been obtained at 25°C for concentrations ranging from 1 to 12×10−2 mol. dm−3. From intensity measurements of the νS-O (A1) stretching vibrations at 1050 cm−1 (free HSO4−) and 1010 cm−1 (bonded HSO4−), the ionic dissociation coefficient is evaluated. The association constant is 42.6 mol.dm−3. At the studied concentrations no multiple ion aggregates can be detected in the solution.

The infrared spectrum of matrix isolated pyridine and pyridine-d5 is studied in noble gas matrices. A number of vibration band splittings is observed, most of which have not yet been reported in literature. The splittings are found to be caused by two types of association, a pyridine-pyridine one and a pyridine-H2O complex. Information concerning the structure of the associated systems is obtained from a careful analysis of the experimental results.

The conformational landscape of N-acetylcysteine (NAC) has been investigated by a combined experimental matrix-isolation FT-IR and theoretical methodology. This combination is a powerful tool to study the conformational behavior of relatively small molecules. Geometry optimizations at the HF/3-21 level resulted in 438 different geometries with an energy difference smaller than 22 kJ mol−1. Among these, six conformations were detected with a relative energy difference smaller than 10 kJ mol−1 at the DFT(B3LYP)/6-31++G∗∗ level of theory. These were finally subjected to MP2/6-31++G∗∗ optimizations which resulted in five minima. The vibrational and thermodynamical properties of these conformations were calculated at both the DFT and MP2 methodologies. Experimentally NAC was isolated in an argon matrix at 16 K after being sublimated at 323 K. The most stable MP2 form appeared to be dominant in the experimental spectra but the presence of three other conformations with ΔEMP2

A 3-aminopropyltrimethoxysilane-derived self-assembled monolayer (NH 2 SAM) is investigated as a barrier against copper diffusion for application in back-end-of-line (BEOL) technology. The essential characteristics studied include thermal stability to BEOL processing, inhibition of copper diffusion, and adhesion to both the underlying SiO 2 dielectric substrate and the Cu over-layer. Time-of flight secondary ion mass spectrometry and X-ray spectroscopy (XPS) analysis reveal that the copper over-layer closes at 1-2-nm thickness, comparable with the 1.3-nm closure of state-of-the-art Ta/TaN Cu diffusion barriers. That the NH 2 SAM remains intact upon Cu deposition and subsequent annealing is unambiguously revealed by energy-filtered transmission electron microscopy supported by XPS. The SAM forms a well-defined carbon-rich interface with the Cu over-layer and electron energy loss spectroscopy shows no evidence of Cu penetration into the SAM. Interestingly, the adhesion of the Cu/NH 2 SAM/SiO 2 system increases with annealing temperature up to 7.2 J m -2 at 400°C, comparable to Ta/TaN (7.5 J m -2 at room temperature). The corresponding fracture analysis shows that when failure does occur it is located at the Cu/SAM interface. Overall, these results demonstrate that NH 2 SAM is a suitable candidate for subnanometer-scale diffusion barrier application in a selective coating for copper advanced interconnects.

The symmetry-broken geometry and variation of metal composition of semishells induce new plasmonic properties. A system of separated metallic semishells embedded in a poly(dimethylsiloxane) polymer film provides an ideal platform to investigate the localized surface plasmon resonance modes of semishells. We demonstrate experimentally that silver, gold, copper, and aluminum semishells can offer distinct plasmonic responses due to the wide range of their material parameters. Numerical calculations combined with the plasmon hybridization theory render us a clear understanding and assignment of the plasmonic modes of the semishells.

The focusing of plasmons to obtain a strong and localized electromagnetic-field enhancement for surface-enhanced Raman scattering (SERS) is increasing the interest in using plasmonic devices as molecular sensors. In this Full Paper, we report the successful fabrication and demonstration of a solid-state plasmonic nanoslit-cavity device equipped with nanoantennas on a freestanding thin silicon membrane as a substrate for SERS. Numerical calculations predict a strong and spatially localized enhancement of the optical field in the nanoslit (6 nm in width) upon irradiation. The predicted enhancement factor of SERS was 5.3 x 10(5), localized in an area of just 6 x 1.5 nm(2). Raman spectroscopy and imaging confirm an enhancement factor of approximately 10(6) for SERS from molecules chemisorbed at the nanoslit, and demonstrate the electromagnetic-field-enhancing function of the plasmonic nanoantennas. The freestanding membrane is open on both sides of the nanoslit, offering the potential for through-slit molecular translocation studies, and opening bright new perspectives for SERS applications in real-time (bio)chemical analysis.

Dynamic light scattering (DLS) is an analytical tool used routinely for measuring the hydrodynamic size of nanoparticles and colloids in a liquid environment. Gold nanoparticles (GNPs) are extraordinary light scatterers at or near their surface plasmon resonance wavelength. In this study, we demonstrate that DLS can be used as a very convenient and powerful tool for gold nanoparticle bioconjugation and biomolecular binding studies. The conjugation process between protein A and gold nanoparticles under different experimental conditions and the quality as well as the stability of the prepared conjugates were monitored and characterized systematically by DLS. Furthermore, the specific interactions between protein A-conjugated gold nanoparticles and a target protein, human IgG, can be detected and monitored in situ by measuring the average particle size change of the assay solution. For the first time, we demonstrate that DLS is able to directly and quantitatively measure the binding stoichiometry between a protein-conjugated GNP probe and a target analyte protein in solution.

Gold (Au) nanoshells are known to exhibit many attractive optical properties caused by the excitation of localized surface plasmon resonances (LSPRs). Reducing the symmetry of these nanoshells has a number of interesting consequences, such as exciting different plasmon modes, making the optical response angle-dependent, and enhancing the local electric field intensity. In this paper, a versatile procedure involving ion milling has been developed to fabricate reduced-symmetrical Au semishells. This allows us to precisely control the reduced-symmetrical geometry and, particularly, the upward orientation of the created nanoaperture. These features, along with a combination of finite different time domain (FDTD) calculations, suggest Au semishell monolayer structures for a potential application in surface-enhanced Raman spectroscopy (SERS)-based biomolecule detection. Au semishells, additionally, exhibit advantageous features over Au nanoshells, for example, a more pronounced red shift of LSPR bands by tuning...

Self-assembled monolayers (SAMs) are investigated as potential Cu diffusion barriers for application in back-end-of-line (BEOL) interconnections. A screening of SAMs derived from molecules with different head group (SiCl"3, Si(OCH"3)"3, Si(OCH"3)Cl"2) bonding to the dielectric substrate, chain lengths (n=3-21) and terminal group (CH"3, Br, CN, NH"2, C"5H"4N and SH) bonding to the Cu overlayer are compared in terms of inhibition of interfacial Cu diffusion and promotion of Cu-SiO"2 adhesion. SAM barrier properties against Cu silicide formation are examined upon annealing from 200 to 400^oC by visual inspection, sheet resistance measurements (Rs) and X-ray Diffraction Spectroscopy (XRD). Cu/SAM/SiO"2 adhesion is evaluated by tape test and four-point probe measurements. Results indicate that NH"2-SAM derived from 3-aminopropyltrimethoxysilane is the most promising for Cu diffusion barrier application. Silicide formation is inhibited to at least 400^oC, essential stability for BEOL integration. However, the 2.9Gc (J/m^2) adhesion of the layer compared with 3.1Gc (J/m^2) on SiO"2 does need improvement.

Three-dimensional (3D) self-assemblies of metal nanoparticles (NPs) are attracting intense attention for sensing applications since they display unique optical properties which are distinct from their respective bulk and individual NP characteristics. In this paper, 3D self-assembled gold (Au) NPs multilayer structures have been fabricated by the alternate deposition of a bifunctional cross-linker and Au NPs, to improve the refractive index sensitivity of the localized surface plasmon resonance sensor. UV–vis spectroscopy, atomic force microscopy (AFM) and cross-section transmission electron microscopy (TEM) have been used to characterize the obtained multilayer structures. The investigations show that the number of Au NP deposition cycles has a strong effect on the sensitivity of the sensor and the multilayer structure fabricated from four NP deposition cycles exhibits maximum sensitivity to the change of the environmental refractive index.

The paper presents the conformational, vibrational and hydrogen bond characteristics of 5-methyl-3-nitro-2-hydroxyacetophenone studied with the combined matrix-isolation FT-IR spectroscopic and theoretical (DFT/B3LYP/6-31++G ∗∗ ) technique. Theoretical calculations predict three stable conformations of the studied compound. Only two of these conformations could be identified experimentally using the matrix-isolation FT-IR technique. The conformation with the intramolecular hydrogen bond OH … O N has been found to be more stable than the conformation with the OH … O C type of hydrogen bond by 7.28 kJ/mol. The complete assignment of the experimental spectra could be performed based on the theoretical calculations including the normal coordinate analysis and isotopic substitution.

Modifying the surface of magnetic nanoparticles (MNPs) to allow for controlled interaction with biomolecules enables their implementation in biomedical applications such as contrast agents for magnetic resonance imaging, labels in magnetic biosensing or media for magnetically assisted bioseparation. In this paper, self-assembly of trialkoxysilanes is used to chemically functionalize the surface of γ-Fe2O3@SiO2 core-shell particles. First, the silane deposition procedure was optimized using infrared analysis in order to obtain maximum packing density of the silanes on the particles. The surface coverage was determined to be ∼8 × 1014 molecules/cm2. It was shown that the magnetic, crystalline, and morphological properties of the MNPs were not altered by deposition of a thin silane coating. The optimized procedure was transferred for the deposition of aldehyde and poly(ethylene glycol) (PEG) presenting silanes. The presence of both silanes on the particle surface was confirmed using XPS and FTIR. The interaction of proteins with silane-modified MNPs was monitored using a Bradford protein assay. Our results demonstrate that, by introducing aldehyde functions, the MNPs are capable of covalently binding human IgG while retaining their specific binding capacity. Maximum surface coverage occurs at 46 μg antibodies per mg article, which corresponds to 35 antibodies bound to an average sized MNP (54 nm in diameter). The human IgG functionalized MNPs exhibit a high degree of specificity (∼90%) and retained a binding capacity of 32%. Using the same approach, streptavidin was coupled onto the MNPs and the biotin binding capacity was determined using biotinylated fluorescein. At maximum surface coverage, a biotin binding capacity of 1500 pmol/mg was obtained, corresponding to a streptavidin activity of 76%. On the other hand, by introducing PEG functions the non-specific adsorption of serum proteins could be significantly suppressed down to ∼3 μg/mg. We conclude that self-assembly of silane films creates a generic platform for the controlled interactions of MNPs with biomolecules.

FT-IR and FT-Raman spectra of the ortho -hydroxy acylaromatic Schiff bases (2-(α-( N -methylimino)ethyl)-4-chloro-6-nitrophenol – I , 2-(α-( N -methylimino)ethyl)-4,6-dichlorophenol – II ), and their isotoposubstitutions have been recorded in the range of 4000–50 cm −1 . The spectra were interpreted by a normal coordinate analysis based on B3LYP/6-31++G(d,p) density functional calculations and experimental deuterosubstitution. Proton transfer equilibrium between the enolic and keto tautomers of two sterically hindered Schiff bases has been studied combined experimental (FT-IR matrix-isolation and FT-Raman) and theoretical (DFT/B3LYP/6-31++G(d,p)) methods.

The optimal geometries, energies, polarities, infrared frequencies, and intensities of the non-polar and polar conformers of 1,3,5-triacetylbenzene were calculated using DFT/B3LYP/6-311G** and semi-empirical (AM1 and PM3) methods. All the methods revealed that the non-polar conformer prevails in vacuum. The infrared spectra in the solid state, in Ar matrix, and in liquid solutions as well as the dipole moments of 1,3,5-triacetylbenzene in many solvents show the distinct influence of the environment on the non-polar conformer ⇌ polar conformer equilibrium. The effect of solvent polarity on the standard Gibbs energy of this conformational equilibrium is quantitatively discussed in terms of the continuum-homogenous dielectric model.

Magnetic particles (MPs) have been attracting much interest as a labeling material for advanced biological and medical applications, such as biomagnetic separation, drug delivery, magnetic resonance imaging, and hyperthermia. In most of these applications, the MPs have been designed to specifically interact with a target, such as cells or proteins, moving freely in a solution. However, for surface-based applications, such as magnetic biosensing, these MPs must bind specifically with a target that is immobilized onto a planar substrate. Consequently, new interaction phenomena, which influence the binding of the MPs to the substrate, have to be taken into account. To achieve adequate binding characteristics and to optimize the MPs toward substrate labeling, these physicochemical interactions should be properly identified. In this paper, the interactions between 16 commercially available streptavidin MPs and a biotinylated gold substrate were monitored in real time by surface plasmon resonance technology and the particle surface coverage was calculated by optical microscopy. On the basis of the type of interactions, the MPs studied in this paper could be classified into three different cases: (I) MPs that bind to the biotinylated substrate via the specific streptavidin-biotin interactions, without showing any nonspecific interactions; (II) MPs that do not bind to the substrate; and (III) MPs that bind to the biotinylated substrate via nonspecific interactions rather than via specific streptavidin-biotin interactions. The three cases were understood by determining the surface charges of both the particle and the substrate in ζ potential measurements. It was found that binding of MPs to the substrate was strongly dependent on the amount and the sign of the charges on both surfaces. The strong influence of electrostatic interactions was validated by simulating the total interaction force between a streptavidin MP and a biotinylated substrate by use of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, while the gravitational force and the streptavidin-biotin force were accounted for. Finally, we conclude that apart from a well-controlled streptavidin coating, the surface charge of the particle and the substrate plays a pivotal role in the construction of MP assays on surfaces.

Experimental and theoretical studies were carried out in order to investigate the rotational isomerism of terephthalaldehyde. The dipole moment measurements and infrared spectroscopy in Ar matrix and using various solvents were performed experimentally. In order to supplement the experimental study, both static and dynamical theoretical calculations were performed. IR spectra and potential energy distribution (PED) were calculated for both cis and trans isomers of terephthalaldehyde in gas phase using B3LYP/6-31G(d,p) level of theory. Further calculations consisted of conformational analysis were performed in order to estimate the rotational barrier and relative stabilities of isomers. The DFT theory with B3LYP functional and four double-zeta and triple-zeta basis sets served as framework for this part of calculations. Semiempirical AM1 and PM3 methods were also used for gas-phase modeling. Molecular dynamics using MM3 force field was applied to study the preferences of solvent molecules’ orientation around the studied molecule. Additionally, the effect of solvent polarity on the Gibbs energy of the trans ⇌ cis equilibrium was analyzed in terms of the continuum dielectric medium models.

Conformational analysis of 2,2′-dinitrobiphenyl (DNBP) performed at the B3LYP/6-31G level of theory has shown that the most stable form in vacuo is the conformer with the torsional angle of ϕ = 81.6°. The theoretical simulations and the experimental dipole moments measurements have revealed that the molecular geometry of DNBP is distinctly modified by the medium. The torsional angle ϕ gradually decreases with increasing dielectric permittivity of the solvent.

FT-IR Ar-matrix isolated spectra were studied for dichloro- (Cl 2 -MB) and tetrachloroderivatives (Cl 4 -MB) of the ortho Mannich base. The spectra were analyzed based on the DFT calculated frequencies and intensities and compared with those recorded in CCl 4 solution in the region of the ν (OH) and ν (OD) vibrations. The matrix-isolated spectra are characterized by narrower ν (OH) and ν (OD) bands with much better resolved fine structure than in solution. The fine structure originates from the anharmonic coupling with the low frequency modes as well as from Fermi resonance. The ν (OD) band shapes can be reproduced exclusively by assuming the Fermi resonance with overtones and summation of the frequencies of modes into which the bridge atoms are involved. The frequency isotopic ratio (ISR) is for both compounds 1.33 while the half-width ratios are equal to 1.82 and 1.94, for Cl 2 -MB and Cl 4 -MB, respectively.

The complicated conformational isomerism of tyrosine is studied by experimental matrix-isolation FT-IR spectroscopy combined with theoretical DFT(B3LYP)/6–31 ++ G ** calculations. Not less than 18 possible conformations of tyrosine have been considered theoretically. The results revealed that the most and the less stable forms of neutral tyrosine have the same conformation of the main part of amino acid (conformation II) but they differ in orientation of the phenyl ring. The calculated values of the relative energies suggest that all conformations would be detectable in the experimental spectrum. However, it appeared that it is not possible to distinguish in the experimental spectrum between the bands due to the forms with the same conformation of the main part of amino acid but a different orientation of the phenol ring.

This paper investigates the influence of molecular size and hydrophobicity of dissolved organic compounds in aqueous solution on retention. In a first part, the influence of hydrophobicity was investigated for organic molecules with a similar molecular weight below the molecular weight cut-off (MWCO) of the membrane and a different hydrophobicity, expressed by the logarithm of the octanol–water partition coefficient (log P). A good correlation was found between the hydrophobicity and the retention: molecules with a high log P (hydrophobic) generally had a low retention, while molecules with a negative log P (hydrophilic) showed a high retention. This could be explained by hydration of the molecules. In a second part, the correlation between the retention of molecules with a molecular weight above the MWCO of the membrane and their hydrophobicity was studied. It was found that a high hydrophobicity lowers the retention, but the influence of hydrophobicity decreases if the molecular size (compared to the MWCO of the membrane) increases. Finally, the influence of adsorption on retention was investigated. An increase in permeate concentration and thus a decrease of the corresponding retention, as a function of time, was observed for hydrophobic compounds, until saturation of the membrane was reached (steady-state retention).

The conformational equilibria of neutral serine are studied by experimental matrix-isolation Fourier transform infrared spectroscopy in combination with density functional theory (DFT) calculations. The geometries and energies of the low-energy conformers of serine were optimized using the DFT(B3LYP)/6-31++G** method. In addition, we calculated the infrared frequencies and intensities of the most stable conformers in order to assist in the assignment of the vibrational bands in the experimental spectrum. The calculated relative energies suggest that four conformers are sufficiently stable to appear in the gas phase and all could be distinguished in the experimental matrix infrared spectra. We also calculated theoretical rotamerization constants and compared these with experimental determined constants. For the equilibria SER2/SER1 and SER3/SER1, a deviation between the experimental rotamerization constant and the theoretical constant was found. A relatively strong intramolecular H-bond in conformers SER2 ...

Photochemical syn–anti isomerizations were studied for N 4 -methoxycytosine and 1-methyl- N 4 -methoxycytosine isolated in argon or nitrogen low-temperature matrices. Upon UV ( λ>295 nm ) irradiation photoconversion of the syn isomers into the corresponding anti forms was observed. This demonstrates that, although the syn–anti photoisomerization concerns rotation of a large methoxyl group, steric interactions with the matrix cage do not preclude it. The final stage of the reaction was a photostationary state. Subsequent UV ( λ>335 nm ) irradiation led to photoisomerization in the opposite direction, resulting in partial recovery of the syn isomers of the investigated N 4 -methoxycytosines.

The H-bond interaction of the adenine with HCl is investigated using the combined matrix-isolation FT-IR and theoretical density functional theory. Theoretical calculations indicate that three closed complexes of the type III (proton transfer or ion pair H-bond), each containing two hydrogen bond, i.e., N 1 + –H⋯Cl − ⋯H–NH; N 3 + –H⋯Cl − ⋯H–N 9 and N 7 + –H⋯Cl − ⋯H–NH, have been obtained. The experimental spectra are consistent with this prediction.

In a number of applications, e.g. DNA/protein micro-array technology, enzyme-linked immunosorbent assay (ELISA) technology or surface plasmon resonance (SPR) technology, the covalent coupling of proteins to surfaces is required. Following the covalent coupling of proteins, the remaining reactive groups should be blocked in order to avoid covalent binding of the analyte to the reactive surface. To this end, preferably blocking agents containing groups that avoid nonspecific adsorption should be used. These blocking agents are typically ethanolamine and cysteine for protein coupling via amino groups and thiol groups, respectively. This report presents novel blocking agents containing poly(ethylene oxide) (PEO) groups. These blocking agents show enhanced qualities to avoid nonspecific adsorption and can therefore have advantages in versatile protein-surface technologies.

The absorption spectrum of noble metal spherical nanoparticles is known to be strongly influenced by the dielectric constant of the surrounding material, and as such, these particles are well suited for biosensing applications. To perform biosensing using nanoparticles on a substrate, the metal particles are covalently attached onto quartz using an organic adhesion layer of mercaptosilanes. The particles in solution are characterized by UV-vis spectroscopy and transmission electron microscopy, while those attached to the quartz are characterized with UV-vis spectroscopy and atomic force microscopy. Antibodies are attached to the metal nanoparticles, and the antigen recognition is monitored via the change of light absorption when this binding event occurs. Not only is the absorbance originating from plasmon resonances of the particles influenced by the dielectric properties of molecules attached to the nanospheres but also the interband absorption of the particles changes, which will be demonstrated in this report. A light absorption change is detected when a molecular recognition occurs between the bioreceptor molecules attached to the nanoparticle and a biomolecular counterpart. This change in absorption can be very large when adhered molecules are at resonance (interband transitions). In addition, the presented type of biosensing can be a cost-effective and easy to use alternative to conventional biosensing techniques. ispartof: Analytical chemistry vol:75 issue:24 pages:6894-6900 ispartof: location:United States status: published

This paper reports the surface modification of hydrophilic γ-Al2O3/anatase-TiO2 multilayer membranes by a silane coupling treatment, in order to obtain NF membranes applicable in non-polar solvents. Special care was given to optimization of the pore structure of the anatase toplayer (microporous–mesoporous) and selection of the reaction medium (ethyl acetate) and silane coupling reagent ((CH3)2SiCl2, C1 silane; C8H17CH3SiCl2, C8 silane). Hexane and water permeability were studied before and after silane treatment as an indication of the effect of the modification. No hexane permeability was obtained before modification. For microporous membranes fired at 300 °C, the internal pore structure remained hydrophilic upon silane treatment, as evidenced by the fact that the hexane permeability remained zero. On the contrary, the more open membrane structure with mesopores obtained by firing at temperatures higher than 400 °C, could be modified by a silane coupling reaction at the internal pore structure. The ratio of permeability, hexane/water, was altered from 0/1 for a firing at 300 °C and a C1 silane treatment to 1/0 for a firing at 500 °C and a C8 silane treatment. Standard PEG-retention measurements in water showed that the membranes fired at 400 and 450 °C and modified with a C8 and C1 silane, respectively, have pore sizes corresponding to those of nanofiltration (NF) membranes. These membranes were characterized by a molecular weight cut-off (MWCO) of 410 and a hexane permeability of 3 l h−1 m−2 bar−1 (400-C8) and a MWCO of 650 and a hexane permeability of 5 l h−1 m−2 bar−1 (450-C1).

Correlations between experimental and DFT(B3LYP)/6-31++G ∗∗ calculated parameters for a series of closed H-bonded complexes of type X⋯HO⋯HN between a water molecule and a purine or pyrimidine base are investigated. Regular relationships are observed between: (1) the calculated H-bond distance and the H-bond angle; (2) the frequency shift, −Δ ν OH b (experimental and theoretical) and the X⋯H distance/the elongation of the OH bond; (3) the experimental relative frequency shift, Δ ν (NH⋯)/ ν ° (NH) and the calculated interaction energy; and (4) the experimental and the calculated frequency shift, −Δ ν OH b . All the X⋯HO⋯HO complexes used in this work correlate similarly in all relationships, although the nature of the different H-bond-acceptor groups, i.e. X=N, O or S, is clearly expressed in some of the correlations.

An affinity biosensor interface of a biosensor is the interface between the sample and the transducer surface and is therefore of the utmost importance for the general performance of a biosensor. For immunosensor applications the affinity biosensor interface consists of antibodies, which are preferably covalently attached to the transducer surface. In this paper the properties and the enhanced performance of an affinity biosensor interface based on mixed self-assembled monolayers (SAMs) on gold are discussed. Mixed SAMs consist of two different functionalities, which allow attachment of bioreceptor molecules and avoid nonspecific adsorption. In this work, mixed SAMs of thiols with carboxylic and hydroxyl or poly(ethylene glycol) groups are characterized with contact angle measurements, cyclic voltammetry, and grazing-angle Fourier transform infrared spectroscopy. It is found that the various mixed SAMs exhibit acceptable coverage and structural properties. Most importantly, surface plasmon resonance measurements clearly show the enhanced performance of these mixed SAMs with regard to sensitivity, stability, and selectivity compared to commercially available affinity biosensor interfaces. This superiority is experimentally demonstrated by evaluating the amount of immobilized antibodies, the recognition of antigens by the immobilized antibody, and the nonspecific adsorption of IgG molecules on the antibody-coated surfaces. ispartof: Langmuir vol:19 issue:10 pages:4351-4357 status: published

Relations between selected experimentally observed matrix isolation FT-IR and/or DFT(B3LYP)/6-31++G** predicted parameters are investigated for a series of 1:1 water complexes of pyridine and imidazole derivatives. Regular correlations are observed for: (i) the experimental and calculated OH stretching frequency shifts; (ii) the ratio between the observed and calculated IR stretching frequencies of the water OH group involved in the hydrogen bond and the proton affinity of the hydrogen bonding site (N atom) of the base; (iii) the H-bond interaction energy and the OH stretching frequency shift; (iv) the calculated OH and N⋯H distances and the interaction energy of the H-bond; and (v) the interaction energy of the H-bond and the square root of the intensity enhancement of the OH stretching mode. These correlations are restricted to structurally similar systems (i.e. to the pyridine or the imidazole analogs). These correlations demonstrate that the DFT(B3LYP) method is very suitable to predict trends in the parameters related to the H-bonding.

The chemical stability of multilayer alumina and titania nanofiltration (NF) membranes, prepared by a sol–gel procedure was investigated. The membranes have toplayers of γ-AlOOH fired at 400 °C, anatase–TiO2 fired at 300 °C and anatase–TiO2 fired at 450 °C, respectively. The solvent stability of the membranes was proven in a series of stability tests with different types of organic solvents. In order to provide information about the corrosion properties, the membrane performance (PEG-retention, molecular weight cut-off (MWCO), permeability) was studied in a series of dynamic corrosion tests with aqueous solutions at low pH (HNO3) and at high pH (NaOH). For the membrane with a γ-AlOOH toplayer (low crystallinity), the MWCO increased from 200 to 1700 after 7 days of operation at pH 2, indicating serious membrane corrosion. For the anatase–TiO2 membrane fired at 300 °C (low crystallinity), the MWCO increased from 200 to 800 at pH 2. On the contrary, corrosion tests performed with the highly crystalline anatase–TiO2 membrane fired at 450 °C demonstrated no significant loss in membrane performance in the pH range studied (1.5–13). Long-term corrosion tests (6 weeks) at pH 2 and 1.5 confirmed the high corrosion resistance for this type of NF membrane.

The tautomeric, vibrational, and H-bonding characteristics of N4-methoxycytosine (N4MC) are investigated by a combined experimental, matrix-isolation Fourier transform infrared spectroscopic and computational study. For the theoretical part of the study, the methods RHF, MP2, and DFT(B3LYP) are used with the 6-31++G** basis set. N4MC occurs in a low-temperature Ar matrix exclusively in the oxo-imino form. Two isomers of this tautomer exist. Using IR intensities of characteristic bands, an approximate value of 2.3 × 10-2 is obtained for the isomerization constant KI (anti/syn). Theoretically, two closed H-bonded complexes with water are found for both isomers, i.e., N1−H...O−H...OC2 and N3−H...O−H...OC2, as well as one less stable open complex, N7...H−O and O8...H−O, for the syn and anti isomer, respectively. In the experimental FT-IR spectra, both closed H-bonded complexes are clearly identified based on characteristic H-bonding absorptions predicted by the calculations. Trace amounts of the open complexe...

This paper reports the characterization of a multilayer TiO 2 membrane, consisting of two mesoporous anatase interlayers and a microporous anatase top-layer, prepared by a sol–gel procedure. A molecular weight cut-off (MWCO) in the range 500–600 and a permeability of 20 l h −1 m −2 bar −1 was demonstrated. In order to provide information about the membrane charge, a detailed study was made of zeta potential and salt retention. Five types of salts were considered: NaCl, KCl, LiCl, Na 2 SO 4 , CaCl 2 . Experiments with mono-monovalent salts revealed the amphoteric character of the membrane material with an IEP around pH 6. The membrane showed a minimal salt retention at pH 6 and a fairly high retention at alkaline pH ( R (NaCl) = 85%, R (KCl) = 87%, R (LiCl) = 90%). For salts containing divalent ions, zeta potential measurements showed the effect of selective SO 4 2− or Ca 2+ adsorption on the membrane charge. In retention experiments with these salts, the correlation between experimentally determined zeta potential and retention behaviour is demonstrated. Depending on the pH of the salt solution and the acquired membrane charge, high retentions were again achieved ( R (Na 2 SO 4 ) > 95%; R (CaCl 2 ) = 78%).

An experimental and theoretical RHF, MP2 and DFT/6-31++G** study is described of the matrix FT-IR spectra of monomer 2-aminopurine and H-bonded complexes of 2-aminopurine with water. 2-aminopurine occurs in Ar predominantly as the amino-N9H tautomer, but small amounts of the amino-N7H tautomer are also present. An approximate KT value for this tautomeric equilibrium is found to be 0.016 (RHF) and 0.015 (DFT) using the infrared intensity measurement. Four H-bonded complexes of the abundant amino-N9H form with water are detected in the experimental FT-IR spectrum by their characteristic predicted absorptions, i.e. the three closed complexes N3 ... H-O ... H-N9, N1 ... H-O ... H-NH, N3 ... H-O ... H-NH and the open complex N7 ... H-OH. From the experimental results, the proton affinity of the N7 atom in 2-aminopurine can be estimated. The dependence of the H-bond strength on the H-bond linearity is demonstrated by a correlation between the N ... H distance and the N ... H-O angle in closed N ... H-O ... H-N complexes.

The preparation and characterization of porous ceramic multilayer nanofiltration (NF) membranes is described. During preparation, special care was given to each sub-layer that forms a part of the multilayer configuration: the macroporous substrate, the membrane interlayers and the NF toplayers. High-quality macroporous supports are prepared from α-Al 2 O 3 . Three types of colloidal sol–gel derived mesoporous interlayers are considered: Al 2 O 3 , TiO 2 and mixed Al 2 O 3 –TiO 2 . The active NF toplayer is a very thin and fine textured polymeric TiO 2 toplayer. Optimized α-Al 2 O 3 /γ-Al 2 O 3 /anatase and α-Al 2 O 3 /anatase/anatase multilayer configurations show high retentions for relatively small organic molecules (molecular weight cut-off 2 O 3 layers is restricted to mild aqueous media (pH 3–11) or non-aqueous media (organic solvents). For NF applications in aqueous media with a lower or higher pH, the multilayer membrane composed of anatase on a α-Al 2 O 3 support is to be preferred.

Results of X-ray diffraction, IR spectra of the solute either in an Ar matrix or in benzene and carbon tetrachloride solutions as well as DFT theoretical studies are used to discuss the structure and dynamics of 4-chloro-2′-hydroxy-4′-ethoxyazobenzene with particular attention to the OH⋯N intramolecular hydrogen bonding. The packing in the crystalline lattice suggests preferences for the formation of sandwich type dimers in stacks with OH⋯N bridges in two opposite directions. The analysis of the IR spectra supported by DFT calculations was particularly devoted to the manifestations of hydrogen bonding in the ν(OH) and γ(OH) vibrations. It is demonstrated that there is a substantial contribution of the γ(OH) overtone to the intense complex absorption in the spectral region around 1600 cm −1 . The mechanical and electrical anharmonicities of the OH group are discussed based on the H/D frequency and intensity isotope effects. The extremely small intensity of the ν(OH) band (41 km mol −1 ) is also particular in the present case.

The H-bonding interaction between the oxopurine base hypoxanthine and water is investigated using matrix-isolation FT-IR spectroscopy combined with theoretical density functional theory and ab initio methods. For vibrational frequency predictions, only the DFT/B3-LYP method is used, while for the prediction of relative energies and H-bond interaction energies of the complexes, four different theoretical methods are compared, i.e., RHF//RHF, MP2//RHF, DFT//DFT, and MP2//DFT. The oxo-N1HN7H, the oxo-N1HN9H, and the hydroxy-N9H (rotamer with the hydroxy-H atom pointed toward the N1 atom) are found to be the three most stable tautomeric forms of the free base. Different, stable complexes between these three tautomers and water have been predicted theoretically. The experimental FT-IR spectra agree well with this prediction, and most of the characteristic spectral data for the four most stable closed complexes, N7H···OH···OC6 and N1H···OH···OC6 of the O17 tautomer and N1H···OH···OC6 and N9H···OH···N3 of the O1...

We studied in detail the chemical structure evolution of Pb(Zr1−x, Tix)O3 (PZT) thin films on Pt electrodes during the initial thermal steps of their preparation using an alkoxide-based sol-gel process. Absorption-reflection Fourier transform infrared spectroscopy (AR-FTIRS) was used to monitor chemical reactions occurring in the films on a real temperature scale. We demonstrate that the chemical state of the pyrolyzed film strongly depends on pyrolysis conditions and can have a large effect on the orientation selection in the film. First, residual acetate groups, resulting from incomplete decomposition of the Pb acetate precursor, strengthen the (111) PZT texture component after crystallization. Second, OH bonds, which are seen to remain in the film after pyrolysis under specific conditions, are seen to strengthen the intensity of the PZT(100) reflection. Possible mechanisms behind these observations are discussed.