Reflection Absorption FTIR Spectroscopy Research Articles

Underpotential deposition of Nickel on platinum single crystal electrodes

The initial stages of nickel electrodeposition on platinum single crystal electrodes have been investigated using cyclic voltammetry and CO charge displacement. While at pH=1, nickel deposition is not visible in the voltammogram, regardless of the crystal orientation, at buffered solutions with pH>3, nickel presence in solution produces clear voltammetric peaks around 0.35V RHE on Pt(111) and Pt(110). Conversely, no clear voltammetric peaks are observed at any of the studied pHs on Pt(100). CO charge displacement experiments suggest that deposited nickel is in the form of a nickel hydroxide. Coulometric analysis is used to deduce the stoichiometry of the deposited adlayer. Moreover, the effect of nickel presence on CO oxidation has been investigated and the CO adlayer characterised using FTIR reflection absorption spectroscopy.

Formation, characterization and corrosion protection efficiency of self-assembled 1-octadecyl-1H-imidazole films on copper for corrosion protection

A film of 1-octadecyl-1H-imidazole (OI) has been formed on copper surface by the self-assembly technique. The optimum concentration of OI and immersion period for the formation of protective OI film have been established using electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS), reflection absorption FTIR spectroscopy, atomic force microscopy (AFM), and contact angle measurements have been used to characterize the OI film on copper surface. The efficiency of OI film to protect copper from corrosion in aqueous NaCl environment has been investigated using EIS, potentiodynamic polarization studies, cyclic voltammetry, scanning electron microscopy (SEM) and weight-loss studies. All these studies showed that the OI film offers excellent protection against corrosion of copper. The mechanism of corrosion protection of copper by the OI film is discussed.

Self-assembled 1-octadecyl-1H-1,2,4-triazole films on copper for corrosion protection

A film of 1-octadecyl-1H-1,2,4-triazole (OTA) was formed on a fresh copper surface by self-assembly technique. The optimum concentration of OTA and immersion time for the formation of a protective OTA film have been established using electrochemical impedance spectroscopy (EIS). These are (i) 15mM concentration of OTA in methanol and (ii) immersion period of 48h. X-ray photoelectron spectroscopy (XPS), reflection absorption FTIR spectroscopy, atomic force microscopy (AFM), and contact angle measurements have been used to characterize the OTA film on copper surface. The efficiency of OTA film to protect copper from corrosion in aqueous NaCl environment has been investigated using EIS, potentiodynamic polarization studies, cyclic voltammetry and weight-loss studies. All these studies showed that the OTA film affords excellent protection against corrosion of copper.

Temperature effect on the surface phase transitions of monolayer films of C12E1 at air/water interface

The temperature-dependent conformational states of a monolayer film of ethylene glycol monododecyl ether (C12E1) at the air/water interface have been investigated using ellipsometry, surface tension, external reflection–absorption FTIR spectroscopy and two-dimensional infrared (2DIR) correlation analysis. The ellipticity coefficients and the entropy associated with C12E1 adsorption changed almost discontinuously at certain temperatures, which manifested the interfacial phase transitions. The phase transition and coexistence of two phases were further clarified using 2DIR correlation analysis with temperature perturbation. The asynchronous correlation maps revealed that both bands of asymmetric and symmetric C–H stretching vibration in one-dimensional IR were split into two components, which confirmed the coexistence of two phases at the interface.

Adsorption and detection of Escherichia coli using an Au substrate modified with a catecholate-type artificial siderophore–Fe3+ complex

A catecholate-type artificial siderophore with a terminal-NH2 group (1) and its Fe(3+) complex (2) were prepared. Siderophore 1 was characterized by (1)H NMR, FT-IR, and ESI-TOF MS spectroscopy. The corresponding Fe(3+) complex 2 was obtained by reaction of 1 with Fe(acac)3. The absorption band at 500 nm (ε = 4670 M(-1) cm(-1) at pH 7.0) of the electronic absorption spectrum of 2 is assignable as the LMCT (O(catecholate) → Fe(3+)) absorption band. This band indicates the formation of the Fe(3+) complex of 1. The biological activity of 2 with respect to Escherichia coli was clearly confirmed by observing that it permeates into the cell membrane. The self-assembled monolayer of 2 on an Au substrate, 2/Au, was prepared and its preparation was confirmed by FT-IR reflection-absorption spectroscopy (IR-RAS) and cyclic voltammetry (CV). Furthermore, a quartz crystal microbalance (QCM) chip modified with 2 effectively adsorbed E. coli. M. flavescens, an organism which is incapable of synthesizing siderophores and must therefore use exogenous hydroxamate-type siderophores for growth, did not adsorb on 2/Au. In contrast, E. coli did not adsorb on the hydroxamate-type artificial siderophore-Fe(3+) complex (3)-modified Au substrate, 3/Au. These results provide preliminary evidence that microbes recognized Fe(3+) ion-bound siderophores on the surface. The detection limit of 2/Au was ∼10(4) CFU mL(-1).

PM-IRRAS studies of the adsorption and stability of organophosphonate monolayers on passivated NiTi surfaces

Alkylphosphonic acids of different alkyl chain lengths were adsorbed on electrochemically polished NiTi surfaces from ethanolic solutions. The electropolishing process led to passive films mainly composed of Ti-oxyhydroxide. The surface showed nanoscopic etching pits with a depths of about 2 nm and a diameter of about 20 nm. The interfacial binding mechanism of the phosphonic acid group to the oxyhydroxide surface and the ordering of the monolayer were spectroscopically analysed by means of infrared reflection absorption FTIR-spectroscopy with (PM-IRRAS) and without (IRRAS) photoelastic modulation. The comparison of IRRAS and PM-IRRAS data of the long chain octadecylphosphonic acid monolayer proved that the binding mechanism of the phosphonic acid group to the oxyhydroxide surface is based on a mono- or bidentate bond, which is not stable in the presence of high water activities. An alkyl chain length of 17 CH 2 groups is required for the formation of self-assembled monolayers, which are stable in aqueous environments. These long chain aliphatic organophosphonic acid monolayers were shown to inhibit anodic and cathodic surface reactions.

Electrochemical and surface analytical studies of the self-assembled monolayer of 5-methoxy-2-(octadecylthio)benzimidazole in corrosion protection of copper

5-Methoxy-2-(octadecylthio)benzimidazole (MOTBI) monolayer was self-assembled on fresh copper surface obtained after etching with nitric acid at ambient temperature. The optimum conditions for formation of self-assembled monolayer (SAM) were established using impedance studies. The optimum conditions are methanol as solvent, 10 mM concentration of the organic molecule and an immersion period of 24 h. The MOTBI SAM on copper surface was characterized by contact angle measurements, X-ray photoelectron spectroscopy and reflection absorption FTIR spectroscopy and it is inferred that chemisorption of MOTBI on copper surface is through nitrogen. Corrosion protection ability of MOTBI SAM was evaluated in aqueous NaCl solution using impedance, electrochemical quartz crystal nanobalance, potentiodynamic polarization and weight-loss studies. While bare copper showed a charge-transfer resistance (Rct) value of 1.89 kΩ cm2 in 0.20 M NaCl aqueous environment, the Rct value for SAM covered copper surface is 123.4 kΩ cm2. The MOTBI SAM on copper afforded corrosion inhibition efficiency of 98–99% in NaCl solution in the concentration range and in the temperature range studied. The SAM functions as a cathodic inhibitor. Quantum chemical calculations showed that MOTBI has relatively small ΔE between HOMO and LUMO and large negative charge in its benzimidazole ring, which facilitate formation of a polymeric [Cu+-MOTBI] complex on copper surface.

Surface plasmon resonance spectroscopic chiral discrimination using self-assembled leucine derivative monolayer

Pirkle-type chiral stationary phases (CSPs) showed excellent enantiomeric separation for amino acid derivatives by forming energetically different two transient diastereomeric π–π donor–acceptor complexes with two enantiomers. A CSP derived from N-(3,5-dinitrobenzoyl) leucine with a thiol ending group for immobilization on Au was synthesized and self-assembled on Au surface as chiral sensing layer. The monolayer characterized by spectroscopic and microscopic methods such as AFM, FTIR reflection absorption spectroscopy (FTIR-RAS) and cyclic voltammetry (CV). The enantiospecific detection onto CSP of the leucine derivative was studied by surface plasmon resonance (SPR). ( S)-CSP SAM showed high chiral differential detection for ( S)-analyte in a range of 1.0 × 10 −9 to 1.0 × 10 −4 M. In combination with the SPR method, the leucine derivative monolayer provided a reliable and simple experimental platform for enantiospecific detection.

Reversible molecular recognition–removal cycles at a thymine-containing ionically crosslinked polyallylamine film

Reversible molecular recognition–removal cycles of 2,4,6-triaminopyrimidine (TAP) based on complementary triple hydrogen bonding were achieved at a cast thin film consisting of a thymine-containing ionically crosslinked polyallylamine (P(TS)C18), based on evidence from FTIR reflection absorption spectroscopy. By immersing the film in a 15 mM TAP aqueous solution at room temperature, approximately 80% of the maximum recognition amount was achieved within 5 min, and the recognition was almost saturated in 1 h. The adsorbed TAP was almost completely removed by immersion of the film in pure water at 60 °C for 30 min. Successive cycles of such recognition–removal behavior were carried out with high reproducibility. Simultaneously with the recognition, the packing structure of the long alkyl chains in the film was also found to change from the orthorhombic to the hexagonal structure, reverting to the orthorhombic structure as the guest molecules were removed from the film. The excellent reversibility of recognition–removal cycles observed for the P(TS)C18 film is thought to be due to the film structure being flexible and stable enough to make spaces for incorporation of the guest molecule in the film matrix.

1P-224 リン脂質と色素の複合薄膜のFTIR反射吸収スペクトロスコピーと表面構造観察(生体膜/人工膜・構造物性,第46回日本生物物理学会年会)

1P-224 リン脂質と色素の複合薄膜のFTIR反射吸収スペクトロスコピーと表面構造観察(生体膜/人工膜・構造物性,第46回日本生物物理学会年会)

Utilizing ultrathin DNA/poly-lysine multilayer films to create liquid/liquid interfaces:spectroscopic characterization, interfacial reactions and nanoparticle adsorption

Alternating electrostatic multilayer adsorption of poly-L-lysine (pLys) and DNA is used tocreate well-defined biopolymer multilayers for use as an ultrathin aqueous phase inliquid–liquid interfacial measurements. The molecular structure and thickness of thepolyelectrolyte multilayers are determined using a combination of polarizationmodulation FT-IR reflection-absorption spectroscopy (PM-FTIRRAS) and FT-surfaceplasmon resonance (FT-SPR) thickness measurements. Electroactive species such asferri/ferrocyanide ions can be incorporated into the DNA/pLys polyelectrolytemultilayers. The ion transport activity of these electroactive films when in contact with1,2-dichoroethane is verified by electrochemical measurements. Micron-sized patterns ofthese multilayers are created by either photopatterning, vapour-deposited spot patterningor microfluidic stencil processing, and are used in conjunction with fluorescence andsurface plasmon resonance imaging (SPRI) to monitor (i) the intercalation ofdye molecules into DNA/pLys ultrathin films, (ii) the electrostatic adsorption ofgold nanoparticles onto DNA/pLys multilayers and (iii) the spatially controlledincorporation and reaction of enzymes into patterned biopolymer multilayers.

Chemical composition and barrier properties of Ag nanoparticle-containing sol–gel films in oxidizing and reducing low-temperature plasmas

Silver nanoparticle-containing silica sol–gel coatings were synthesised using tetraethylorthosilicate (TEOS), HNO 3 and AgNO 3 as the main precursors and 3-(2-aminoethylamino)propyl trimethoxysilane (DIAMO) as a stabiliser. The stability and the barrier properties of the coatings were studied by means of UV/Vis spectroscopy, FTIR reflection absorption spectroscopy (IRRAS), spectroscopic Ellipsometry and electrochemical impedance spectroscopy (EIS). Both the long-term stability and barrier properties of the coatings could be tailored by low-temperature O 2 and H 2-plasma treatments. The oxidative plasma treatment enabled the change of the matrix from organic–inorganic to silica-like and the reductive treatment led to a reduction of the formed passive film on the Ag nanoparticles within the matrix. Thereby, based on the combination of sol–gel chemistry with subsequent plasma treatment new thin film functionalities can be achieved.

Anodic decomposition of citric acid on gold and stainless steel electrodes: An in situ-FTIR-spectroscopic investigation

The electrochemical decomposition of citric acid on gold and stainless steel AISI 304 (18% Cr, 10% Ni) electrodes was investigated using the technique of in situ InfraRed Reflection Absorption FTIR Spectroscopy (IRRAS) in combination with cyclic voltammetric measurements. The applied potential sweep starts from −0.265 up to +2.5 V on gold and from +0.4 up to +2.4 V on steel electrodes. The initial potentials of the anodic decomposition of citric acid could be observed on both electrode materials. Carbon dioxide was detected as decomposition product. Using stainless steel electrodes, the decarboxylation of citric acid and the forming of citrate complexes were observed. The consumption of citric acid is both due to its anodic decomposition and the generation of soluble citrate complexes of iron, nickel and chromium, resulting from the transpassive dissolution of the electrode material. At potentials more positive than +500 mV both processes are occurring simultaneously.

Surface Plasmon Resonance Imaging Measurements of Antibody Arrays for the Multiplexed Detection of Low Molecular Weight Protein Biomarkers

This paper describes a simple methodology for the creation of high-density multiplexed antibody arrays on gold surfaces that can be used to detect low molecular weight protein biomarkers with surface plasmon resonance imaging (SPRI). A one-step carbonyldiimidazole (CDI) surface reaction was utilized to attach antibodies onto alkanethiol-modified gold surfaces and characterized with polarization modulation FT-IR reflection absorption spectroscopy. The CDI chemistry was then employed to create an antibody microarray with array element sizes varying from 750 microm down to 200 microm. As a demonstration, a three-component antibody array was employed to detect two clinically important protein biomarkers, beta2-microglobulin (11.8 kDa) and cystatin C (13.4 kDa). SPRI measurements could simultaneously detect both of these small unlabeled proteins with no cross talk at solution concentrations from 300 nM down to 1 nM. In addition, the adsorption strengths of these biomarkers onto an antibody array were measured with SPRI and compared to those obtained from the kinetic analysis of single-channel angle shift SPR measurements.

Surface Phase Transition of C12E1 at the Air/Water Interface: A Study by Dynamic Surface Tension, External RA FT-IR, and 2D IR Correlation Methods

The surface conformational states of the Gibbs monolayer of ethylene glycol mono-n-dodecyl ether (C(12)E(1)) at the air/water interface was studied using dynamic surface tension, external reflection-absorption FT-IR spectroscopy (ERA FT-IR), and two-dimensional infrared (2D IR) correlation methods at constant temperature. The dynamic surface tensions were measured at different bulk concentrations of C(12)E(1), and it was observed that a constant surface tension region appears at approximately 38.5 mN m(-1) in a dynamic surface tension profile at concentrations higher than 11 micromol kg(-1). This constant surface tension region corresponds to the surface phase transition from liquid expanded (LE) to liquid condensed (LC). Two sets of ERA FT-IR spectra were collected, one at different bulk concentrations but after equilibrium time (equilibrium measurements) and another at constant bulk concentration (m = 16 micromol kg(-1)) but at different times (dynamic measurements). The first set of these measurements show that the peak area increases in the range of 11 < m < or = 16 micromol kg(-1), which means the increase in the number of surfactant molecules at the air/water interface. Also, the wavenumber of antisymmetric CH(2) stretching decreases gradually from approximately 2923 cm(-1) (for 10 and 11 micromol kg(-1)) to approximately 2918 cm(-1) (for m > or = 16 micromol kg(-1)) with increasing concentration. The wavenumbers of 2923 and 2918 cm(-1) were assigned to LE and LC phases, respectively, and the decrease of wavenumber in the concentration range of 11 < m < or = 16 micromol kg(-1) were correlated to the surface phase transition (LE --> LC), or in other words, in the mentioned concentration range, two phases coexist. The dynamic ERA FT-IR measurements at 16 micromol kg(-1) also confirm the surface phase transition from LE to LC. The 2D IR correlation method was applied to the both equilibrium and dynamic IR spectra of the C(12)E(1) monolayer. The synchronous correlation maps show two strong autopeaks at approximately 2922 and approximately 2851 cm(-1) and also show a strong correlation (cross-peaks) between antisymmetric CH(2) stretching (nu(a)) and symmetric CH(2) stretching (nu(s)). The asynchronous correlation maps show that both observed bands of nu(a) and nu(s) in one-dimensional IR split into two components with the characteristic of overlapped bands, which reveals the coexistence of two phases (LE and LC) at the interface at 11 < m < or = 16 micromol kg(-1). The synchronous and asynchronous maps that were obtained from dynamic IR spectra closely resembled the equilibrium map.

Uptake of Small Oxygenated Organic Molecules onto Ammonium Nitrate under Upper Tropospheric Conditions

The uptake of formic (C1), propanoic (C3), butanoic (C4), and pentanoic (C5) acids onto ammonium nitrate (AN) has been investigated as a function of temperature and relative humidity using a Knudsen cell flow reactor coupled with FTIR-reflection absorption spectroscopy (FTIR-RAS). The uptake of acetone and methanol onto AN was also briefly studied. Initial uptake coefficients (gamma) were determined over the temperature range 200-240 K. Formic, propanoic, and butanoic acids exhibited efficient but temperature-dependent uptake on AN, with larger uptake coefficients observed at lower temperatures. Pentanoic acid was not taken up by AN under any of the conditions studied. Uptake of acetone and methanol onto AN was observed, but in insignificant amounts under atmospherically relevant conditions. Infrared spectra revealed that propanoic and butanoic acids ionized on the surface, despite the fact that the AN films were effloresced. Formic acid reacted with the AN film to produce ammonium formate and ionized nitric acid. Adding small amounts of water vapor (4% RH) to the chamber resulted in dramatically increased gamma values for all of the acids. Furthermore, the IR spectra showed the formation of a liquid layer when propanoic and butanoic acids adsorbed on the surface at RH = 20% and greater. Liquid water features were not observed at a similar relative humidity in the absence of the acids. These results show that small organic acids can be efficiently scavenged by AN and lead to enhanced water uptake under upper tropospheric conditions.

Spectroscopic analysis of the interface chemistry of ultra-thin plasma polymer films on iron

The bonding of organosilanes to iron surfaces was analysed on three model samples using FTIR-reflection absorption spectroscopy (IRRAS) for the layer characterisation and ToF-SIMS to characterise specific fragments that are commonly interpreted as the proof for a covalent +Si–O–Me-bonding. On an ultra-thin HMDSO plasma polymer coated specimen, characteristic fragments of a covalent bonding of organosilanes to iron oxide surfaces as discussed by other authors could be reproduced, whereas on the pure iron substrate no such peaks could be observed. On an iron surface dip-coated from a diluted polydimethylsiloxane solution, the discussed characteristic fragments of a covalent bonding could be found. This arises questions on the validity of the common interpretation, since in the case of pure physical adsorption of a non-reactive long-chain siloxane, no such bonds should be detectable. Additionally, ToF-SIMS sputter depth profiles on the HMDSO plasma polymer coated iron surface and of the iron surface covered with polydimethylsiloxane could be shown to behave qualitatively identical.

Combination of FTIR reflection absorption spectroscopy and work function measurement for in-situ studies of plasma modification of polymer and metal surfaces

An in-situ plasma cell for low and atmospheric pressure plasma treatment of polymer and metal substrates was developed. It enables the investigation of the sample surface with FTIR spectroscopy at grazing incidence as well as the simultaneous measurement of the volta potential difference between the outmost surface layer and a reference electrode in vacuum or a defined atmosphere. To demonstrate the benefits of the device, the plasma modification of a model polymer and an oxide covered metal surface has been investigated. It could be shown that even sub-monolayer surface changes, e.g., the etching of the CH3 and CH2 groups and the generation of carbonyl functions on an octadecylmercaptane (ODM) self-assembly monolayer on gold in a low-pressure oxygen plasma can be detected. Moreover, plasma induced changes of the oxidation states of iron and the thickness and composition of its oxide or oxyhydroxide layer could be monitored. The presented applications of this new in-situ analytical device prove that the measurement of work function in combination with monolayer sensitive vibrational spectroscopy provide new insight in plasma induced surface modifications.

Fabrication of polycondensed multilayer thin films by a self-assembly method

Polycondensed thin films which had a high-ordered structure were fabricated from dicarboxylic acid and diamines using N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) as condensing agents by a self-assembly method. In this study, adipic acid (ADA) or 9,11-docosadiyn-1,20-dicarboxylic acid (DDyDA) were selected for dicarboxylic acid, and 4,4′-diaminodiphenylmethane dihydrochloride (DAM) for diamine parts. UV–vis and quartz crystal microbalance (QCM) measurements were used to monitor the layer-by-layer deposition process. FT-IR reflection absorption spectroscopy (FT-IR-RAS) was also carried out in order to confirm the polycondensation of monomers. These results indicated that dicarboxylic acid and diamines were alternately deposited and polymerized with condensing agents on nano-scale. In addition, polydiacetylene network was successfully incorporated in DDyDA system by γ-irradiation due to the high ordered structure.

Compactness evaluation of amorphous and nanocrystaline thin films by FT-IR reflection–absorption spectroscopy

A method based on FT-IR near-grazing-incidence-angle reflection–absorption spectroscopy and the phenomenon of the Berreman effect was developed for the estimation of the compactness or density of thin films. The testing of the method was performed on amorphous and nanocrystaline Cu-oxide thin films, which were prepared on Au covered glass and Si wafer substrates by wet chemistry route using dip-coating technique. The density of the film was used as a parameter, which was adjusted in the simulation calculation until the sufficient agreement between calculated and experimental near-grazing angle reflection spectra was achieved. The results showed the increase in density of Cu-oxide films with repeated dip-coating cycles. This was in agreement with the observation of the microstructure with TEM and SEM.