Quantification of free and weakly bound cyanide in water using infrared spectroscopy.

We report a simple method for the detection of polyatomic anions in water. The approach involves precipitation of the polyatomic anion using simple monoatomic cations followed by collection of the particles on an infrared transparent membrane for quantification by infrared spectroscopy. The approach is demonstrated with the detection of free and weakly bound cyanide in water.

A simple solution to the problem of selective detection of phosphate and arsenate by the molybdenum blue method.

We report a simple and fast method for the quantification of both phosphate and arsenate in water using the molybdenum blue method. The method does not require established pre-treatment procedures for physically separating arsenate and phosphate or reducing the arsenate to arsenite. In our method, the heteropolymolybdate ions in the solution are precipitated and collected on a membrane that is transparent in both the visible and infrared regions of the spectrum.

A new approach for measuring water concentration in oil using copper sulfate powder and infrared spectroscopy.

An approach for measuring water concentration in oil, based on the use of CuSO particles and infrared spectroscopy, is described. The particles interact with both dissolved water and water droplets to form the monohydrate, CuSO·HO. These particles are collected on an infrared transparent membrane and then an infrared spectrum in transmission mode is recorded.

Measurement of water concentration in oils using CaO powder and infrared spectroscopy.

A simple method for measuring water concentration from 1 to 10000 mg L is described. The approach involves adding CaO powder to an oil sample and measuring the amount of Ca(OH) produced by the reaction of CaO with water. Collection of the powder occurs by passing a fixed volume of the oil through an infrared transparent membrane and the amount of water is determined from the intensity of the OH stretching mode of Ca(OH) at 3645 cm.

A solventless method for detecting trace level phosphate and arsenate in water using a transparent membrane and visible spectroscopy.

The molybdenum blue method is the American Public Health Association (APHA) approved method for the detection and quantification of phosphate in water. The standard molybdenum blue method, APHA 4500 PE has a detection limit of 30 μgL phosphate (10 μgL phosphorus) in freshwater with a 5 cm cuvette. To further lower the detection limit to sub μgL levels, we have developed a simple, fast, and solventless method for conversion of phosphate present in solution to a solid for quantification by Visible spectroscopy.

A reagentless and rapid method to measure water content in oils.

A simple method for measuring water levels from 1 mg L to 5000 mg L in oils that uses no chemical reagents or matrix specific calibrations is described. The approach involves capturing the water from the oil on an infrared transparent membrane and then recording an IR spectrum in transmission mode through the membrane. A classic spectrum of liquid water is obtained for all oil types, as both dissolved water and emulsion-based water are extracted to form an adsorbed layer of water on the membrane surface.

Controlled growth of layer-by-layer assembled polyelectrolyte multilayer films under high electric fields.

Hypothesis: The application of an external electric Field (E-Field) to control layer-by-layer (LBL) growth of polyelectrolyte multilayers (PEM) typically involves hydrolysis of the water at the electrodes. We hypothesize that by isolating the electrodes from contact with the water, high E-Fields could be used to control the conformation of the polyelectrolytes in the solution phase and thus, enable non-chemical control of the LBL growth.

Experimental: Attenuated total reflectance infrared spectroscopy was used to monitor the bound fraction and adsorbed amount as a function of time for the sequential addition of polyacrylic acid and polydiallyldimethylammonium chloride adsorbed on a TiO film under the applied E-Field.

Photodegradation of taste and odor compounds in water in the presence of immobilized TiO-SiO photocatalysts.

Disinfection by ultraviolet (UV) radiation is a growing trend in public water treatment systems because of its effectiveness with respect to inactivation of protozoa and other pathogenic microorganisms. However, removal of different classes of organic compounds, including taste and odor compounds in water is not effective with UV irradiation. In this study, a novel TiO-based immobilized photocatalyst is developed to enhance the UV photodegradation of two of the major taste and odor compounds, 2-methylisoborneol (MIB) and Geosmin (GSM) in water.

Supercritical Fluid Atomic Layer Deposition: Base-Catalyzed Deposition of SiO2.

An in situ FTIR thin film technique was used to study the sequential atomic layer deposition (ALD) reactions of SiCl4, tetraethyl orthosilicate (TEOS) precursors, and water on nonporous silica powder using supercritical CO2 (sc-CO2) as the solvent. The IR work on nonporous powders was used to identify the reaction sequence for using a sc-CO2-based ALD to tune the pore size of a mesoporous silica. The IR studies showed that only trace adsorption of SiCl4 occurred on the silica, and this was due to the desiccating power of sc-CO2 to remove the adsorbed water from the surface.

Dynamics of layer-by-layer growth of a polyelectrolyte multilayer studied in situ using attenuated total reflectance infrared spectroscopy.

Attenuated total reflectance infrared spectroscopy (ATR-IR) was used to study the dynamic layer-by-layer (LBL) growth of a sodium polyacrylate (NaPA)/poly(diallydimethylammonium) chloride (PDADMAC) multilayer on TiO2 particles. Molecular weights (Mw) used were 30 and 60 kDa for NaPA and 8.5 and 150 kDa for PDADMAC.

Molecular dynamics of the interaction of anionic surfactants with liposomes.

The time dependent molecular interactions of sodium dodecyl sulfate (SDS) with dipalmitoylphosphatidylcholine (DPPC) liposomes were studied using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. In particular, the ATR spectra provided information on the dynamic amount of SDS incorporated and DPPC expelled in the DPPC structure along with structural information on the molecular nature of the SDS/DPPC assemblies. It was found that the uptake of SDS was always mirrored by the ejection of DPPC molecules from the liposomes and that the incorporation of SDS followed two routes; SDS intercalated into the DPPC liposomes and SDS was bound electrostatically to the charged surface of the DPPC liposome.

An infrared spectroscopic based method for mercury(II) detection in aqueous solutions.

A new method that uses solid phase extraction (SPE) coupled with FTIR spectroscopy to detect Hg(II) in aqueous samples is described. The technique is envisioned for on-site, field evaluation rather than lab-based techniques. This paper presents the "proof of principle" of this new approach toward measurements of Hg(II) in water and identifies mass transport issues that would need to be overcome in order to migrate from a lab based method to field operation.

A comparison of the behavior of cholesterol, 7-dehydrocholesterol and ergosterol in phospholipid membranes.

A molecular description of the effect of incorporation of cholesterol (CHOL), 7-dehydrocholesterol (7DHC) and ergosterol (ERGO) on the structure of DPPC or EggPC liposomes is provided. Data obtained from ATR-IR spectroscopy, detergent solubility and zeta potential measurements show that the insertion of the various sterols alters the packing arrangement of the tails and headgroup of the PC lipids and may lead to lipid domain formation. On a molecular basis, the differences in lipid packing architecture are traced to differences between the ring and tail structure of the three sterols and these differences in structure produce different effects in DPPC liposomes in the gel phase and EggPC liposomes in the fluid phase.

Detection of spores using electric field-assisted FTIR-ATR.

An approach that integrates an electric field with an attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) flow through cell was used to detect spores in aqueous environments. A "proof of concept" in terms of the principle features of the method is described. It is shown that under an electric field, the negatively charged spores migrate and are concentrated on the surface of a ZnSe internal reflection element (IRE).

Detection of Bacillus globigii spores using a Fourier transform infrared-attenuated total reflection method.

The use of an alumina-coated ZnSe internal reflection element (IRE) to detect spores by attenuated total reflection infrared spectroscopy (FTIR-ATR) was investigated. Two methods for coating the IRE with alumina are described. It is shown that the adsorption proceeds through an interaction of the carboxylate groups on Bacillus globigii (BG) and positively charged sites on the alumina.

An infrared spectroscopic based method to measure membrane permeance in liposomes.

A new method for studying membrane permeance in liposomes is described. The method uses liposomes fabricated to contain IR probe molecules with CN moieties in combination with attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. The liposomes are adsorbed on a TiO2 coated ATR crystal and remain intact to flowing aqueous solutions.

Dual WO(3) based sensors to selectively detect DMMP in the presence of alcohols.

A size selective approach to improving selectivity in semiconducting metal oxides (SMO) sensors was obtained by tailoring the architecture of WO(3) powders. The key for achieving high selectivity is based on using a dual sensor configuration where the response on a porous WO(3) powder sensor was compared to the response on a nonporous WO(3) powder sensor. Detection selectivity between methanol and dimethyl methylphosphonate (DMMP) is obtained because the access of a gas molecule in the interior pore structure of WO(3) is size dependent leading to a size dependant magnitude change in the conductivity of SMO sensor.

Live cell adhesion assay with attenuated total reflection infrared spectroscopy.

Living confluent fish fibroblast cells RTG-P1 from rainbow trout adherent on diamond were examined by attenuated total reflection (ATR) infrared (IR) spectroscopy. In particular, IR spectra were recorded dynamically during the adsorption of the cells onto the diamond and during their biochemically induced structural responses to the subsequent addition of trypsin and cytochalasin D. It is shown that changes in the IR spectra result from changes in cell morphology and surface coverage.

Inaccessible hydroxyl groups on silica are accessible in supercritical CO2.

The three main types of hydroxyl groups on a silica surface are classified as isolated, hydrogen bonded, and inaccessible. The isolated and hydrogen bonded groups are the most important as these readily exchange with D(2)O and thus are exposed to reactant molecules. However, it has generally been accepted that the inaccessible groups do not participate in surface reactions as only a small fraction of these groups exchange with D(2)O.

Identification of lipid aggregate structures on TiO2 surface using headgroup IR bands.

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the nature of the dipalmitoylphosphatidylcholine (DPPC) aggregated structures adsorbed on TiO(2). DPPC molecules were assembled on TiO(2) using Langmuir-Blodgett (LB) deposition methods or by directly flowing the DPPC liposome solution across the TiO(2)-coated ATR crystal. We found that there is a direct correlation between the intensity and frequency position of the zwitterionic headgroup IR bands and the nature of LB films.

Reaction of silanes in supercritical CO2 with TiO2 and Al2O3.

Infrared spectroscopy was used to investigate the reaction of silanes with TiO2 and Al2O3 using supercritical CO2 (Sc-CO2) as a solvent. It was found that contact of Sc-CO2 with TiO2 leads to partial removal of the water layer and to the formation of carbonate, bicarbonate, and carboxylate species on the surface. Although these carbonate species are weakly bound to the TiO2 surface and can be removed by a N2 purge, they poison the surface, resulting in a lower level of reaction of silanes with TiO2.

A simple FTIR technique for estimating the surface area of silica powders and films.

A simple technique using FTIR spectroscopy to estimate the surface area of porous and non-porous silica powders is presented. The surface area is estimated by comparing the integrated area of the band due to isolated silanol groups on different silicas. We have found that by using a fumed silica as a calibrant, an accuracy of about 7% in the surface area of several silica materials is obtained when compared to the surface area computed by BET nitrogen adsorption techniques.

Templated surfactant readsorption on polyelectrolyte-induced depleted surfactant surfaces.

Changes in the structure of a surfactant adsorbed on oxidized silicon arising from interaction with a polyelectrolyte have been studied using polarized infrared attenuated total reflection spectroscopy. Specifically, the cationic surfactant cetyltrimethylammonium bromide (CTAB) was found to form a highly ordered layer on oxidized silicon at a concentration of 5.5 x 10(-5) M and a pH of 9.

Infrared study of the interaction of charged silica particles with TiO2 particles containing adsorbed cationic and anionic polyelectrolytes.

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the adsorption of charged silica particles onto TiO(2) particles coated with anionic sodium polyacrylate (NaPA) or cationic poly(diallyldimethylammonium) chloride (PDADMAC). To the best of our knowledge, this is the first time that IR spectroscopy has been used to study the interaction of a polymer layer on one particle with a second different particle. The results show that, once adsorbed on the TiO(2) particle, the PDADMAC or the NaPA does not transfer to the silica particles.

Role of water in the atomic layer deposition of TiO(2) on SiO(2).

Atomic layer deposition (ALD) of TiO(2) on SiO(2) powder using sequential addition of TiCl(4) and H(2)O vapors has been investigated by infrared spectroscopy. In the first cycle, TiCl(4) reacts monofunctionally or bifunctionally with surface silanols forming (Si-O-)(n)Ti-Cl(4)(-)(n) (n = 1, 2) species. Subsequent addition of water vapor leads to the hydrolysis of the (Si-O-)(n)Ti-Cl(4)(-)(n) to form a Ti-O-Ti network, and at the same time, some cleavage of Si-O-Ti bonds occurs, regenerating Si-OH in the process.