Alkylphosphonic Acids Research Articles

Preparation, Characterization, and Modeling of α-Zirconium Phosphonates with Ether-Functional Surfaces

Layered α-zirconium(IV) phosphonates were prepared from novel ether-terminal alkyl phosphonic acids, providing nanoplatelets with brush-like polar surfaces. The precursor materials were characterized by NMR, mass spectrometry, and elemental analysis. The derived nanoparticles were examined by XRD, TEM, TGA, and elemental analysis. The experimental compositions were slightly rich in organophosphorus content. In general, the layered materials had good crystallinity, with layer reflections appearing up to (005) and d-spacings consistent with the anticipated α-phase structure. Computer simulations suggest that tailored surface chemistries, including ether functionalities, will offer favorable thermodynamic interactions with polyester polymer matrices.

Functionalization of nickel oxide using alkylphosphonic acid self-assembled monolayers

Self-assembled monolayer formation of alkylphosphonic acids on the native nickel oxide surface has been accomplished. These monolayers are the first formed on the native nickel oxide surface that did not require electrochemical reduction of the surface to metallic nickel. Two different deposition methods, immersion and aerosol spraying, were used to form monolayers on the oxide surface. Both methods led to complete monolayer formation, with the aerosol method requiring shorter deposition time, lower temperature and decreased solution concentration compared to the immersion method. These deposition methods now allow nickel oxide substrates to be functionalized easily. Monolayer formation was investigated by diffuse reflectance Fourier transform infrared spectroscopy, non-contact mode atomic force microscopy, contact angle measurements and matrix-assisted laser desorption ionization mass spectrometry. Furthermore, cyclic voltammetry and electrochemical impedance spectroscopy studies show that the monolayer increased surface resistance to oxidation.

Self-Assembled Monolayers of Alkylphosphonic Acid on GaN Substrates

In this paper we describe the formation and characterization of self-assembled monolayers of octadecylphosphonic acid (ODPA) on epitaxial (0001) GaN films on sapphire. By immersing the substrate in its toluene solution, ODPA strongly adsorbed onto UV/O 3-treated GaN to give a hydrophobic surface. Spectroscopic ellipsometry verified the formation of a well-packed monolayer of ODPA on the GaN substrate. In contrast, adsorption of other primarily substituted hydrocarbons (C n H 2 n+1 X; n = 16-18; X = -COOH, -NH 2, -SH, and -OH) offered less hydrophobic surfaces, reflecting their weaker interaction with the GaN substrate surfaces. A UV/O 3-treated N-polar GaN had a high affinity to the -COOH group in addition to ODPA, possibly reflecting the basic properties of the surface. These observations suggested that the molecular adsorption was primarily based on hydrogen bond interactions between the surface oxide layer on the GaN substrate and the polar functional groups of the molecules. The as-prepared ODPA monolayers were desorbed from the GaN substrates by soaking in an aqueous solution, particularly in a basic solution. However, ODPA monolayers heated at 160 degrees C exhibited suppressed desorption in acidic and neutral aqueous solution maybe due to covalent bond formation between ODPA and the surface. X-ray photoelectron spectroscopy provided insight into the effect of the UV/O 3 treatment on the surface composition of the GaN substrate and also the ODPA monolayer formation. These results demonstrate that the surface of a GaN substrate can be tailored with organic molecules having an alkylphosphonic acid moiety for future sensor and device applications.

Atomic Force Microscopy Studies of Alkyl-Phosphonate SAMs on Mica

The layer formation of phosphonic acids on mica surface as a model system, from aqueous and ethanol solutions has been investigated. The aggregation behavior (critical micelle concentration, cmc) of molecules in the solution phase has been determined by surface tension measurements in order to select the appropriate concentration for the layer formation experiments. Layer formation of self-assembling molecules of alkyl-phosphonic acids has been followed by atomic force microscopy (AFM). Nucleation, growth and coalescence of densely packed islands of phosphonates from ethanol solution have been recorded on mica surface. The structure of islands depends on the length of alkyl-chains. Self-assembly of phosphonates has been also observed from aqueous solution, as presented by octyl-phosphonic acid (OcPA). The height of OcPA islands is 1.46 􀁲 0.22 nm, which is practically equal with the length of molecule (1.4 nm). This shows that OcPA molecules form monolayer height domains on the mica surface.

Microsynthesis and mass spectral study of Chemical Weapons Convention related 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides

AbstractChemical Weapons Convention (CWC)‐related compounds where the phosphorus atom is part of a ring have very limited representation in mass spectral libraries and the open literature. Here we report electron ionization (EI), chemical ionization (CI) and electrospray ionization tandem mass spectrometry (ESI‐MSn) spectra and retention indices for 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides (alkyl C1 to C3) which are new cyclic chemicals covered under the CWC. The EI mass spectra show a pattern of ion fragmentation that is similar to that of other cyclic phosphonates in that loss of the alkylphosphonic acid as a neutral loss is more important than the presence of the protonated alkylphosphonic acid. In contrast to other cyclic phosphonates, the 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides show almost no protonated alkylphosphonic acid and as a result the spectra do not carry the same distinctive signature of the phosphorus–carbon bond that is required for the chemical to be covered under the CWC. Copyright © 2008 John Wiley & Sons, Ltd.

Surface Mediated Synthesis of Unsymmetrical O,O-dialkyl Alkyl Pyrophosphonates using Neutral Alumina: Potential Chemical Weapons Convention Related Compounds

The surface mediated synthesis of unsymmetrical O,O’- dialkyl alkyl pyrophosphonates from O-alkyl alkylphosphonic acid is described. These pyrophosphonates are listed in schedule 2B4 of Chemical Weapon Convention (CWC). The effect of the presence of chromatographic grade of Al2O3on the phosphorylation of a series of alkyl phosphonic acids has also been investigated. For phosphonic acids having different alkyl groups, it was observed that higher yields of the more hindered pyrophosphonates were formed in the presence of Al2O3. This method has an advantage over the conventional methods in terms of easy work-up, reduced reaction time and high yields.

Phosphonic Acid Modification of Indium−Tin Oxide Electrodes: Combined XPS/UPS/Contact Angle Studies

Indium−tin oxide (ITO) electrodes have been modified with both fluorinated alkyl and aryl phosphonic acids [n-hexylphosphonic acid (HPA) and n-octadecylphosphonic acid (ODPA); 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl phosphonic acid (FHOPA), pentafluorobenzyl phosphonic acid (PFBPA), and tetrafluorobenzyl-1,4-diphosphonic acid (TFBdiPA)]. These are modifiers designed to control both wetting properties toward nonpolar molecular solids and to provide a wide range of tunability in effective surface work function. The molecular nature of surface attachment and changes in electronic and wetting properties were characterized by X-ray photoelectron spectroscopy (XPS), UV-photoelectron spectroscopy (UPS), photoelastic modulation infrared reflection−absorption spectroscopy (PM-IRRAS), and contact angle measurements using both water and hexadecane. Interface dipoles from the PA modifiers contribute to shifts in the low kinetic energy regions of UPS spectra (local vacuum level shifts, which translate into change...

Monoesterfication of Alkylphosphonic Acids by DCC-Celite

A solvent-free synthesis of O-alkyl hydrogen alkyl phosphonates was described. Thus, the reaction of alkylphosphonic acids and alcohols (1 mol equiv) with DCC-Celite (2 mol equiv) was carried out at room temperature to 60 °C to give the corresponding monoesters in 80-92% yield (15 examples). The monoesterification with primary and secondary alcohols was completed within 30-45 and 45-60 min, respectively, while tertiary alcohols did not react with alkylphosphonic acids under similar conditions.

Lewis Acid-catalyzed Nucleophilic Addition of Dialkylphosphite to Hydrazones Derived from Benzoylhydrazine and aliphatic ketones

The synthesis of new derivatives 2 of α-hydrazino-(disubstituted)- alkylphosphonic acids by the Lewis acid mediated addition of dialkylphosphite to hydrazones, derived from ben- zoylhydrazine and aliphatic ketones, is described. Reactions were successfully and catalytically promoted by BF3 etherate under mild condition in methylene chloride at room temperature.

Sensitive detection of phosphopeptides by matrix‐assisted laser desorption/ionization mass spectrometry: use of alkylphosphonic acids as matrix additives

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been one of the most powerful tools for analyzing protein phosphorylation. However, it is frequently difficult to detect phosphopeptides with high sensitivity by MALDI-MS. In our investigation of matrix/matrix-additive substances for improving the phosphopeptide ion response in MALDI-MS, we found that the addition of low-concentration alkylphosphonic acid to the matrix/analyte solution significantly enhanced the signal of phosphopeptides. In this study, the combination of methanediphosphonic acid and 2,5-dihydroxybenzoic acid gave the best results. In addition to enhancing the signal of the phosphopeptides, alkylphosphonic acid almost completely eliminated the signals of sodium and potassium ion adducts. We report herein sensitive detection of phosphopeptides by MALDI-MS with the use of alkylphosphonic acids as matrix additives.

Anchoring of sulfur‐containing alkylphosphonic and semifluorinated alkylphosphonic molecules on a polycrystalline aluminum substrate

AbstractSelf‐assembly on a polycrystalline aluminum substrate of two sulfur‐containing alkylphosphonic acids, CH3(CH2)11S (CH2)2PO(OH)2, and CF3(CF2)7(CH2)2S(CH2)2PO(OH)2, has been compared with CH3(CH2)15PO(OH)2. The reaction of the phosphonic head groups with the hydroxyls at the alumina surface to form phosphonates was studied with X‐ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection‐absorption spectroscopy (PM‐IRRAS). Barrier effects of the resulting layers was assessed by electrochemical polarization curves. With the conditions used in the present work for the self‐assembly reaction, it appears that the sulfur‐containing molecules do not perform as well as CH3(CH2)15PO(OH)2 in terms of film quality. Questions are raised about the possibility that the sulfur‐containing molecules could undergo cleavage during surface modification. Copyright © 2008 John Wiley & Sons, Ltd.

DCC–Celite hybrid immobilized solid support as a new, highly efficient reagent for the synthesis of O-alkyl hydrogen alkylphosphonates under solvent-free conditions

An efficient and solvent-free synthesis of O-alkyl hydrogen alkyl phosphonates is described. The methodology involves the condensation of alkyl phosphonic acids using DCC–Celite under solvent-free conditions.

Novel Modified Pyrrole Monomers, 1: Synthesis and Characterization

Different 1-substituted-(pyrrole alkyl)phosphonic acid derivatives have been designed as adhesion promoters to graft polypyrrole layers on several substrates. These compounds contain two reactive, terminal moieties: the phosphonic acid group as anchor to the oxide surface and the pyrrolyl group, which functions as starting unit for surface polymerisation. Both groups are connected by an alkyl spacer ranging from 4 to 12 methylene units. The short- and long-chain derivatives were synthesized for the first time to study their self-assembling properties and their effectiveness to be used as an adhesion promoter for grafting covalently bound polypyrrole layers on oxide substrates. Surfactant-like properties of the long chain derivatives and their behaviour in water for pyrrole polymerization were also investigated, as will be discussed in future papers. In this first paper of the series, the synthesis and characterization of the monomers are presented. The structure of the molecules was proven by 1H-NMR, 31P-NMR and FT-IR spectroscopy. Thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) revealed that the stability of the compound depended on their chain length: the longer the alkyl chain, the more stable the monomer. On the other hand, reactivity decreased with increasing chain length, as proven by cyclic voltammetry measurements (CV).

Field-amplified sample stacking for the detection of chemical warfare agent degradation products in low-conductivity matrices by capillary electrophoresis-mass spectrometry

Preconcentration of chemical warfare agent degradation products (alkylphosphonic acids and alkyl alkylphosphonic acids) in low-conductivity matrices (purified water, tap water and local river water) by field-amplified sample stacking (FASS) was developed for capillary electrophoresis (CE) coupled to ion trap mass spectrometry. FASS was performed by adding a mixture of HCOONH 4 and NH 4OH in appropriate concentrations to the sample. This allowed to control the conductivity and the pH of the sample in order to obtain FASS performances that are independent of analyte concentration. The influence of different parameters on FASS (sample to background electrolyte (BGE) conductivity ratio, injection volume and concentration of BGE) was studied to determine the optimal conditions and was rationalized by using the theoretical model developed by Burgi and Chien. A good correlation was obtained between the bulk electroosmotic velocity predicted by this model and the experimental value deduced from the migration time of the electroosmotic flow marker detected by mass spectrometry (MS). This newly developed method was successfully applied to the analysis of tap water and local river water fortified with the analytes and provided a 10-fold sensitivity enhancement in comparison to the signal obtained without preconcentration procedure. The quite satisfactory repeatability and linearity for peak areas obtained in the 0.5–5 μg mL −1 concentration range allow quantitative analysis to be implemented. Limits of detection of 0.25–0.5 μg mL −1 for the alkyl alkylphosphonic acids and of 0.35–5 μg mL −1 for the alkylphosphonic acids were reached in tap water and river water.

Micrometer and Nanometer Scale Photopatterning of Self-Assembled Monolayers of Phosphonic Acids on Aluminum Oxide

Self-assembled monolayers of alkylphosphonic acids (APA) have been patterned at the micrometer and nanometer scale by photochemical methods. Exposure of APA monolayers to light with a wavelength of 244 nm leads to scission of the C−P bond and desorption of the alkyl chain from the surface. Immersion of the specimen in a solution of a second APA leads to adsorption at the surface in the exposed regions. Immersion in a solution of hydroxide ions leads to etching of the exposed regions of the aluminum film. UV exposure appears to anneal the aluminum oxide film, conferring increased resistance to etching at high exposures and a switching the function of the monolayer from a positive to a negative tone resist. At intermediate exposures, nanoscale trenches form at the perimeters of exposed regions. Near-field exposure of the phosphonic acid structures, using a UV laser coupled to a scanning near-field optical microscope, yields well-defined nanostructured features following development of the pattern in aqueous base, exemplified by the fabrication of 100 nm wide trenches.

P‐Toluenesulfonic Acid—Celite as a Reagent for Synthesis of Esters of Alkylphosphonic Acids under Solvent‐Free Conditions.

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Study of the Formation of Self-Assembled Monolayers on Nitinol

Shape memory alloys such as nitinol (NiTi) have gained interest due to their unique and unusual properties of thermal shape memory, superelasticity, and good damping properties. Nitinol is mainly used for medical purposes. In order to control the surface properties of this alloy, self-assembled monolayers (SAMs) were formed and characterized on the native oxide surface of nitinol for the first time. Factors which affect the formation of SAMs, such as head group functionality, chain length, and tail group functionality, were varied and analyzed. Functionalized alkyl phosphonic acid molecules (OH, COOH, and CH3) formed monolayers on the nitinol surface using a simple deposition method resulting in the molecules being ordered and strongly bound to the surface. Diffuse reflectance infrared spectroscopy (DRIFT), contact angle goniometry, atomic force microscopy (AFM), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to characterize the surfaces before and after organic modification.

Determination of hydrolytic degradation products of nerve agents by injection port fluorination in gas chromatography/mass spectrometry for the verification of the Chemical Weapons Convention

Retrospective detection and identification of markers of chemical warfare agents are important aspects of verification of the Chemical Weapons Convention. Alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs) are important markers of nerve agents. We describe the development and optimization of a new gas chromatography/mass spectrometry (GC/MS) injection port fluorination method for the derivatization of AAPAs and APAs. The process involved the injection of acids with trifluoroacetic anhydride in GC/MS, where acids are converted into their corresponding volatile fluorides. Various reaction conditions such as fluorinating agent, injection port temperature and splitless time were optimized. The maximum reaction efficiency of the acids with trifluoroacetic anhydride was observed at 230 degrees C injection port temperature with a splitless time of 2 min. APAs showed best analytical efficiencies at 400 degrees C injection port temperature, while the other conditions were similar to those of AAPAs. The linearities of response for APAs and AAPAs were in the range of 1-25 and 5-100 microg mL(-1), respectively, with limits of detection ranging from 500 pg to 800 ng mL(-1).

Infrared Spectra of Alkylphosphonic Acid Bound to Aluminium Surfaces

AbstractSummary: The infrared absorption (IR) spectrum of alkyl phosphonic acid adsorbed on the α‐Al2O3 (0001) surface has been calculated by means of a density‐functional based tight‐binding method. Thereby mono‐dentate, bi‐dentate and tri‐dentate bonding of the acid to the surface have been considered. In addition, experimentally obtained Fourier Transform Infrared Spectra (FTIR) of octadecylphosphonic acid (ODPA) on the natural surface of aluminium have been included. The absence of the PO band in the experimental surface spectrum and in the calculated spectrum of the tridentate adsorption complexes showed that adsorption of (alkyl)phosphonic acids on aluminium favours tridentate bonding, where the acid is bound to the surface via three symmetric POAl bonds.

Synthesis of Specially Designed Adhesion Promoter for Grafting Polypyrrole

AbstractSummary: Adhesion of conducting polymers to the metal/metal oxide surfaces is not strong. An attempt was made to modify these reactive metal surfaces by N‐derivatised pyrroles. ω‐(pyrrol‐1‐yl alkyl) phosphonic acids with different chain lengths were successfully synthesized and characterized. These derivatives were studied for their adsorption and self‐assembling phenomena onto Ti/TiO2, Ta/Ta2O5 and Al/Al2O3. Various analytical tools were used to characterize the modified surface. Contact angle measurements indicated an increase in hydrophobicity after adsorption that was further confirmed by Surface Plasmon Resonance (SPR). X‐ray Photoelectron Spectroscopy (XPS) studies showed that the molecules are oriented in a fashion such that phosphonic acid group is attached to the metal surface and pyrrole is pointing away from the surface. The oxidation potential of these derivatives was higher than pyrrole as expected. Surface polymerisation was successfully attempted on the modified metal substrates. The polymerised surface was examined under Scanning Electron Microscope (SEM). The new compounds not only function as self‐assembling molecules, they also exhibit a new class of reactive functionalized derivatives that can be used as monomers for polymerisation.