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A molecular cooling fan (MF) is a nanocomposite coating technology, where the quantized lattice motions in nanomaterials are assembled to absorb heat from the heat source, promote to higher vibration states, and emit excess energy by radiation. Using a factorial design technique, seven factors were investigated to optimize MF cooling performance and efficiency. The results show that a MF coating prepared with 8 nm sized multiwalled carbon nanotubes can cool down 4 °C lower than that assembled with 50–80 nm due to higher activity of lattice motions. The MF makes equilibrium temperature cool down by 10 and 20 °C at input operation voltages of 35 and 55 V on the same heat dissipation unit (HDU). Using the optimal factors, a MF coating was applied on commercial HDUs. The results demonstrated that molecular fan action can reduce the size and mass of the heat-sink module, offering a low cost LED light unit.

Laser-induced breakdown spectroscopy in composition analysis of materials has many advantages over other analytical methods. Its simple-or-no sampling procedure is a key advantage. The LIBS has been applied to liquid samples, although direct analysis of liquids is difficult because of weak plasma generation. An ion exchange membrane is used in this work to develop a real time monitoring method of metal ions in water. The chelating-resin based filter membrane was used to capture and concentrate copper ions from water. The samples were filtered under reduced pressure for faster filtration. The captured copper ions on the membrane were analyzed by LIBS. A series of copper solutions and mixtures were examined to establish the proper analytical conditions. The plasma emission intensity of copper generated from the thin layer of the membrane was investigated to determine the spectroscopic parameters for a practical real-time water monitoring. The copper ion collected on the membrane can be free of matrix effect from other ions in the original samples, and has provided the consistent analytical results in the mg/L concentration range. The laser power of each ablating pulse is very critical to obtain a proper analytical dynamic range, especially when the copper captured layer is thicker than the depth of one pulse laser can ablate. Tap water was used to analyze and evaluate the feasibility of this method. The amount of copper in the tap water was shown to depend on the retention time of water in copper pipes of the building pluming system.

Four different catalysts, nanodiamond seed, nano-Ni, diamond powder, and mixture of nano-Ni/diamond powder, were used to activate Si wafers for diamond film growth by hot-filament CVD (HFCVD). Diamond crystals were shown to grow directly on both large diamond powder and small nanodiamond seed, but a better crystallinity of diamond film was observed on the ultrasonicated nanodiamond seeded Si substrate. On the other hand, nano-Ni nanocatalysts seem to promote the formation of amorphous carbon but suppress transpolyacetylene (t-PA) phases at the initial growth of diamond films. The subsequent nucleation and growth of diamond crystals on the amorphous carbon layer leads to generation of the spherical diamond particles and clusters prior to coalescence into continuous diamond films based on the CH3 addition mechanism as characterized by XRD, Raman, ATR/FT-IR, XPS, TEM, SEM, and AFM techniques. Moreover, a 36% reduction in surface roughness of diamond film assisted by nano-Ni catalyst is quite significant.

Nanodiamond powder (NDP), multiwall carbon nanotube (MWCNT), and carbon black (CB) were dispersed in an acrylate (AC) emulsion to form composite materials. These materials were coated on aluminum panels (alloy 3003) to give thin coatings. The active phonons of the nanomaterials were designed to act as a cooling fan, termed "molecular fan (MF)". The order of lattice quantization, as investigated by Raman spectroscopy, is MWCNT > CB >> NDP. The enhanced surface emissivity of the MF coating (as observed by IR imaging) is well-correlated to lattice quantization, resulting in a better cooling performance by the MWCNT-AC composite. MF coatings with different concentrations (0%, 0.4%, 0.7%, and 1%) of MWCNT were prepared. The equilibrium temperature lowering of the coated panel was observed with an increase in the loading of CNTs and was measured as 17 degrees C for 1% loading of MWCNT. This was attributed to an increased density of active phonons in the MF coating.

The molecular properties and surface morphology of undoped and N-doped ultra-nanocrystalline diamond (UNCD) films deposited by microwave plasma CVD with addition of nitrogen are investigated with various spectroscopic techniques. The results of spatially resolved Raman scattering, ATR/FT-IR and XPS spectra show more amorphous andsp2/sp3ratio characteristics in N-doped UNCD films. The surface morphology in AFM scans shows larger nanocrystalline diamond clusters in N-doped UNCD films. Incorporation of nitrogen into UNCD films has promoted an increase of amorphoussp2-bonded carbons in the grain boundaries and the size of nanocrystalline diamond grains that are well correlated to the reported enhancement of conductivity and structural changes of UNCD films.

Two algorithms—peak picking and peaks correlation—have been compiled in a portable laser-induced breakdown spectroscopy (LIBS) system and used specifically for spectral fingerprinting of paints and coatings, which contain multiple ingredients and require several application steps. The LIBS technique starts with a laser shot on the specimen surface, detection of the emission of the elements present, and analysis of the sample compositions. The LIBS system has been successfully illustrated for the identification and analysis of coating substrates, surface pretreatments, and primer and topcoat paints obtained in the lab and at field sites. The results indicate that, despite the compositional complexity in organic metal finishing, the spectral fingerprint of paints and coatings can be effectively determined by the LIBS technique. The advantages of LIBS technique over other conventional methods, such as EDX, are that it is quasi-nondestructive (

A sol-gel chemistry approach was used to fabricate nanoparticles of TiO(2) in its anatase form. The particle size is shown to be sensitive to the use of HClO(4) or HNO(3) as acid catalyst. The gold-capped TiO(2) nanocomposites were processed by the reduction of gold on the surface of the TiO(2) nanoparticles via a chemical reduction or a photoreduction method. Different percentages of vanadium-doped TiO(2) nanoparticles, which extended the TiO(2) absorption wavelength from the ultraviolet to the visible region, were successfully prepared. The synthesized nanocomposites have a size of about 12-18 nm and an anatase phase as characterized by XRD, TEM, AFM, and UV-vis spectroscopy. The TiO(2) nanocomposite coatings have been applied on glass slide substrates. The antibacterial activity of TiO(2) nanocomposites was investigated qualitatively and quantitatively. Two types of bacteria, Escherichia coli (DH 5alpha) and Bacillus megaterium (QM B1551), were used during the experiments. Good inhibition results were observed and demonstrated visually. The quantitative examination of bacterial activity for E. coli was estimated by the survival ratio as calculated from the number of viable cells, which form colonies on the nutrient agar plates. The antimicrobial efficiency and inhibition mechanisms are illustrated and discussed.

Two magnetoresistive manganites, La 0.83 Sr 0.17 MnO 3 and La 0.7 Sr 0.3 MnO 3 , are synthesized by the environmentally friendly “deposition by aqueous acetate solution (DAAS)” technique. The manganite film has a grain size of ∼100 nm, and can be processed as thinly as ∼0.03 μm per layer, while the powder form has a crystallite size of ∼40 nm. These magnetoresistive materials are shown to be effective and inexpensive electromagnetic interference (EMI) shield for the extremely low frequency (ELF) EM fields. The electrical resistance of manganites is very sensitive to external influences, such as temperature and electromagnetic fields. Both permeability ( μ ) and conductivity ( σ ) of manganites tend to increase with increasing applied magnetic field. The manganites have been shown to “react” to field increases in a way that is particularly useful for shielding EMI field fluctuations (e.g., due to current or voltage spikes). The manganite properties, e.g., crystal structure, film morphology, radiation absorption and reflection, electrical resistivity, and magnetization, etc., have been measured. The ceramic manganites have a metal–insulator transition at 300 K or higher, and are suitable for a room temperature operation. A thin film (approx. 0.1 μm) of La 0.83 Sr 0.17 MnO 3 was fabricated on a quartz tube or refractory ceramic fiber blanket. Using this thin manganite film, the EMI shielding effectiveness for the measured E -field attenuation is similar to that of a ∼25 μm thickness of copper tube, aluminum foil, and silver–nickel particle-dispersed paper. The silver–nickel impregnated paper has an EMI shielding effectiveness of ∼35 dB at 10 kHz, and ∼15 dB at 60 Hz (or frequency above 1 MHz). The ceramic manganites are chemically inert, thermally stable, and mechanically flexible. They provide low cost EMI shielding against directed energy pulses and may serve as a “signature reduction” barrier.

Six different phosphorus-containing reagents were used as self-phosphating agents and acid catalysts in the formulation of a polyester−melamine coating. The phosphorus compounds chosen for the study were Cycat 4040 (4040), Cycat 296-9 (296), Albright & Wilson PA-75 (PA-75), phosphonosuccinic acid (PPSA), and two in situ phosphatizing reagents (ISPR-1 and ISPR-2, phenylphosphonic acid and fosfosal, respectively). Each individual phosphorus-containing compound was evaluated separately using a varying percentage of agent in the paint formulation. The different paints made using the different modifiers were applied to bare 3003 or 3105 aluminum panels. After the individual phosphorus-containing reagents were optimized, the optimized additives were compared to each other utilizing electrochemical impedance spectroscopy (EIS), differential scanning calorimetry (DSC), saltwater immersion, and pencil hardness tests. The most commonly used acid catalyst (4040) did not perform as well as the other acid catalysts. U...

A pigmentless polyester−melamine coating catalyzed with p-toluenesulfonic acid (p-TSA) shows high impedance (∼1010 Ω·cm2) at low frequency (0.1 Hz). After the addition of pigment and additives, the impedance drops to ∼105 Ω·cm2. However, using an in situ phosphatizing reagent (ISPR) for the dual purpose of catalyzing the polyester−melamine cross-linking reaction and phosphatizing the metal surface does not show this detrimental lowering of the impedance at low frequency. Results of electrochemical impedance spectroscopy measurements and the corresponding electrical equivalent circuits show that the in situ phosphatizing coating (ISPC) applied to both bare and pretreated steel panels provides superior corrosion protection. At low frequency, the panels coated with the ISPC show 1000 times the resistance of the bare and pretreated steel panels coated with the p-TSA-catalyzed polyester−melamine paint. The simultaneous chemical process of the ISPR catalyzing desirable cross-linking reactions and forming the su...

Surface pretreatment, such as chromate conversion, is generally required for the organic coating on Ti-6Al-4V titanium alloys. The surface modification process facilitates bond formation between the titanium surface and adhesives or paints. However, the hexavalent chromate used in the conversion coating is carcinogenic and must be eliminated. Recently, the “green chemistry” technique of in-situ phosphatizing coatings (ISPC) has been developed at Northern Illinois University. In this study, a polyester-melamine coating system catalyzed by p-toluene sulfonic acid is used as a control paint and applied to bare (paint 1) and chromated (paint 3) Ti alloy panels. The arylphosphonic acid employed as an in-situ phosphatizing reagent (ISPR) is used to formulate ISPC polyester-melamine paint and to react in-situ with the metal surface when ISPC paint is applied on bare Ti panels (paint 2) and chromated Ti panels (paint 4). After soaking in 3% NaCl solution for 1500 hr, the electrochemical impedance, |Z|, was measured as 109, 1010, 1010, and 1010 ohm-cm2 for paints, 1, 2, 3, and 4, respectively. After 1000 hr salt spray (fog) testing, a disbondment from the “X” scribe is observed as 13 and

The current organic coating on metals for aerospace applications involves a multi-step process and considerable energy, labor and control, and it generates toxic wastes such as chlorinated solvents, cyanide, cadmium, lead and carcinogenic chromates. The green chemistry technology of in situ phosphatizing coatings (ISPCs) developed in our laboratory is a one-step self-phosphating process, in which the deposition of metal phosphate layer on the substrate surface and the curing of polymer paint film take place independently, but simultaneously. The formation of a metal phosphate layer in situ will essentially eliminate the metal surface pre-treatment step of employing a phosphating line/bath. The use of chemical bonds linked to the paint polymers to seal the pores of metal phosphate in situ should enhance coating adhesion and suppress metal corrosion without a post-treatment of final rinses containing chromium (Cr 6+ ). The successful applications of ISPCs in three types of commercial paints (solvent-borne high-solids, water-reducible and VOC-free latex) on bare and pre-treated cold-rolled steel and 2024 aluminum coupons is presented. The protective performance (coating adhesion and corrosion inhibition) of ISPCs is shown to be superior over that of the current multi-step coating practice.

Toxic chemicals, such as chrome, are commonly used in the application of conversion coatings to various metal surfaces. In situ phosphatizing coatings (ISPCs) are an innovative approach for eliminating the requirement of a conversion coating which ends the need of toxic materials used in a multi-step coating practice. An ISPC is formulated by predispersing an in situ phosphatizing reagent (ISPR) into a paint system. In this study, an ISPR, an arylphosphonic acid, is used in a polyester–melamine paint to react in situ with the metal surface and to provide the acidic catalyst needed, while thermally curing the paint. A second polyester–melamine paint system is used as the control that uses the standard catalyst para-toluenesulfonic acid (p-TSA) to catalyze the cross-linking reaction in the paint. These two paint systems are applied to bare 2024 T3 Al panels and to chromated 2024 T3 Al panels. The coated panels are treated in a corroding media for 2,400 h and monitored periodically using electrochemical impedance spectroscopy (EIS). Results of EIS data and the corresponding electrical equivalent circuit (EEC) show that the ISPC applied to both the chromated and untreated Al panels provide superior corrosion protection. At low frequency (0.01 Hz), the panels coated with the ISPC show 10 000 times more resistance than both the chromated and bare Al panels coated with the control polyester–melamine paint. The corresponding EEC shows that the panels with the control paint applied have double the amount of electrical components (resistors and constant phase elements). A physical interpretation is suggested for the EEC. The paint adhesion to the Al surface and the corrosion behavior are tested by salt-water immersion and salt fog. After the panels are exposed to the salt solution, a pressure tape is applied to test the adhesion. The results show that the ISPC applied on the chromated Al adheres the best. The simultaneous reaction of the ISPR catalyzing the curing of the paint and forming the metal–phosphate layer is the reason for the superior paint performance.

The coating behavior of a polyester−melamine paint catalyzed by an in situ phosphatizing reagent (ISPR) was investigated, and the results were compared to p-toluenesulfonic acid- (p-TSA-) catalyzed paints. Fourier transform infrared spectroscopy was used to ascertain that the reaction between the ISPR and the Al surface takes place. Differential scanning calorimetry was used to measure the glass-transition temperature (Tg) and the Tg thus providing an indication that the ISPR catalyzed the paint film formation. The deterioration of the coatings by overbaking was studied using thermogravimetric analysis. The corrosion resistance of the coatings on aluminum coupons was examined using electrochemical impedance spectroscopy. Equivalent electrical circuits were utilized to give numerical values to the resistors and capacitors in the coated panel. The paint film adhesion was tested by saltwater immersion. The high-quality performance of the ISPR-catalyzed paint can be attributed to the simultaneous reactions of...

We report the successful formulation of stable and compatible in-situ phosphatizing coatings (ISPCs) for a waterborne alkyd-amino baking enamel applied on bare cold-rolled steel (CRS), iron phosphated Bonderite 1000 (BD), and iron phosphated plus Parcolene 60 chromated (BD+P60) coupons. The enhanced coating adhesion of water-based ISPCs is confirmed by the cathodic delamination measurements. After 100 hr of salt spray (fog) test, the corrosion resistance performance (measured by the corrosion disbondment across the “X” scribe, d in mm) of the water-based ISPC on CRS panel (d=4.0−7.0 mm) outperformed that of the control alkyd paint on B-1000 (d=26 mm) and also on BD+P60 (d=14 mm) coupons. The superior coating performance of water-based ISPCs is believed to result from the in-situ metal surface phosphatization as detected by the reflectance FTIR technique.

A single step in-situ phosphatizing coating (ISPC) can be formulated by pre-dispersing an optimal amount of in-situ phosphatizing reagents (ISPRs) into the paint system. The technique of ISPC is applied to a high-solids polyester-malemine baking enamel using a designed “ISPR-2.” The in-can stability of ISPC is verified using rheological measurements. The coating properties and protective performance of the ISPC are compared to those of the multi-step coating of control sample (MCCS). The immersion tests in a 3% NaCl solution and salt spray testings show a significant improvement in paint disbondment from the “X” scribe for ISPC. The observed coating performance enhancement of ISPC over MCCS is confirmed from the multi-functionality of ISPRs. Phosphate chemistry proceeds via an acid-base type of interaction, P-O−- Mn+, and polymer chemistry generates a covalent P-O-C linkage with the polymer network.

The formulation of in-situ phosphatizing coatings (ISPCs) was successfully performed for lacquer systems using a commercial nitrocellulose lacquer and an optimum amount of in-situ phosphatizing reagents (ISPRs). The in-situ phosphatizing lacquer (ISPL) system is stable, and shows no change in surface appearance and drying speed as compared to the unmodified lacquer (UML). The ISPLs are applied on pine, poplar, and red oak wood boards, and on cold-rolled steel, aluminum, and laminated brass panels. Immersion tests in a 3% NaCl solution showed a remarkable enhancement in paint disbonding resistance for the paint film of ISPL on wood and metals compared to that of the UML sample. The paint film protective performance of ISPLs is further evidenced by the lattice pattern tape testings, and by the cathodic delamination and electrochemical impedance spectroscopy.

Ethylenediamine tetraacetic acid (EDTA) was encapsulated in a sol−gel-derived optically transparent glass. The complexation of metal cations, Cu(II), Ni(II), Fe(III), Cr(III), Co(II), Mn(II), Pd(II), and Ir(IV), with EDTA in solutions and in gels was evidenced by the formation of individual colors. A comparison of the absorption spectra of Mn+/EDTA in solution, Mn+/EDTA in gel, and Mn+/EDTA complex in gel was performed. The results show that (i) all six chelating sites in EDTA remain active in a sol−gel matrix as they bind readily with Cu2+, Ni2+, Fe3+, Pd2+, and Ir4+, (ii) EDTA is rigidly oriented in a sol−gel matrix that inhibits its heat- or catalyst-assisted complexation with Cr3+, Co2+, and Mn2+, (iii) no absorption spectral shift for the d−d metal transitions was observed compared to those in solution, yet a 10−30 nm shift for the MLCT transitions of Cu2+, Ni2+, Fe3+, Pd2+, Ir4+ was detected, and (iv) the level of sensitivity in detecting metal cations using EDTA in gel is at least an order of magni...

A novel in-situ phosphating coating system is developed by predispersing an optimum amount of phosphatizing reagents into the paint formulation. Five possible in-situ phosphatizing reagents are used in the formulation of a model solvent-borne polyester-melamine enamel paint system. The new formulation is then coated and cured on a cold-rolled steel surface. The chemical reactivity of phosphatizing reagents are studied via different analytical techniques. The results can be summarized as follows: (i) the phosphatizing reagents, being dispersed into the solvent-borne paints to form a stable self-phosphating organic coating, perform a successful in-situ phosphatization of the metal substrate; (ii) there is an observable lowering of Tg for the paint films, due to the acceleration of melamine self-condensation by the acidic nature of phosphatizing reagents, which can be corrected by optimizing the coating formulation; (iii) the organic phosphatizing reagents, which are more dispersable in a solvent-borne coating system, are very effective yet have less influence on the cross-linking density of the final film, thus giving a coating with higher AC impedance and providing a better corrosion protective performance.

Molecular fan, a radiative cooling by thin film, has been developed and its application for compact electronic devices has been evaluated. The enhanced surface emissivity and heat dissipation efficiency of the molecular fan coating are shown to correlate with the quantization of lattice modes in active nanomaterials. The highly quantized G and 2D bands in graphene are achieved by our dispersion technique, and then incorporated in an organic-inorganic acrylate emulsion to form a coating assembly on heat sinks (for LED and CPU). This water-based dielectric layer coating has been formulated and applied on metal core printed circuit boards. The heat dissipation efficiency and breakdown voltage are evaluated by a temperature-monitoring system and a high-voltage breakdown tester. The molecular fan coating on heat dissipation units is able to decrease the equilibrium junction temperature by 29.1 ° C, while functioning as a dielectric layer with a high breakdown voltage (>5 kV). The heat dissipation performance of the molecular fan coating applied on LED devices shows that the coated 50 W LED gives an enhanced cooling of 20% at constant light brightness. The schematics of monolayer graphene dispersion, undispersed graphene platelet, and continuous graphene sheet are illustrated and discussed to explain the mechanisms of radiative cooling, radiative/non-radiative, and non-radiative heat re-accumulation.

Deposition by the aqueous acetate solution (DAAS) technique was used to synthesize highly crystalline thin films of undoped and 2% iron-doped Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3} [PZT (53,47)] perovskites on sapphire and Pt substrates at 600 C. Fe ions were added either at the precursor stage or diffused thermally. The crystallization of the films was measured by X-ray diffraction. The ferroelectric activity was examined by polarization-voltage hysteresis (P-E) loops. The electro-optical properties of ferroelectric/photoconductive PZT thin films were investigated by excitation photocurrent spectroscopy (EPS) and 77 K emission spectroscopy. The photoconductivity measured at visible wavelengths was enhanced for the thermally diffused, but not the precursor-processed doped materials. This, together with lattice parameters obtained from X-ray data and P-E hysteresis loop measurements, suggested that the precursor-processed doped ions are strongly bonded in the perovskite lattice, whereas the thermally diffused ions are bound more weakly in the grain boundaries.

Excitation photocurrent spectroscopy (EPS) was used to record photoconductivity from 200 to 600 nm for a Pb(Zr0.53Ti0.47)O3 (PZT) thin film. Four spectral bands at 262, 338, and 428/472 nm were obs...

A one-pack paint composition comprising polyester-melamine enamels and a predispersed amount of either phosphoric acid (H 3 PO 4 , in situ phosphatizing reagent), p-toluenesulfonic acid (p-TSA, polymer catalyst), or hydrofluoric acid (HF, surface etching agent) was formulated, coated, and thermally cured on a cold-rolled steel panel. The chemical natures of coating surface/interface were investigated by SEM-EDS and FTIR techniques, and the coating performance was verified by EIS measurements. The formation of metal phosphate layer and covalent bonding of P-O-C linkage at the coating/substrate interface was evident only for the unicoat system formulated with H 3 PO 4

Photocurrent action spectra of Fe-doped PLZT ceramics showed that iron defects enhanced the visible light photoconductivity of PLZT. Long thermal diffusion times increased the dark conductivity. Photocurrent action spectra were used to separate the photocurrent, photovoltaic, dark current, and space charge contributions to the total photocurrent.

The nature of chemical mechanisms, bondings, and structures in a single-step polyestermelamine enamel/H 3 PO 4 systems, in particular, at the interface of polymer/phosphate/steel, was investigated by using ac impedance analysis and 80 o grazing angle reflectance Fourier transform infrared spectroscopy. An in-situ phosphatizing coating on «Q» panel was illustrated and show to behave like a pure capacitance. The «simultaneous» chemical reaction of H 3 PO 4 wth «Q» panel surface and polymer resin was evidenced to produce a corrosion protective barrier by the foration of interfacial layer of crystalline ion phosphate and to enhance coating adhesion by the covalent bondings of P-O-C linkage.

An instrument is developed to evaluate the performance of heat dissipative coatings. The instrument has features to measure the apparent emissivity of a given surface under different input power settings. The emissivity of aluminum (Al Q-panel) and copper, as measured from 60-135 degrees C, showed a value of 0.15+/-0.03 and 0.42+/-0.05, respectively, consistent with reported values in literature. The relative emissivity of a heat dissipative coating, called as molecular fan carbon nanotube "MF-CNT," was found to be approximately 0.97. A simple mathematical model is built to evaluate the role of different heat transfer mechanisms (convection and radiation) on cooling performance, and it was observed that convection plays a dominant role in cooling, with more than 90% of heat transferred by convection. In presence of MF-CNT coating, radiation heat transfer increases to approximately 30% and lowers the steady state temperature by 10 degrees C. It is illustrated that radiative cooling could be a significant factor in thermal management.

An aqueous, metallo-organic precursor for PbTiO3 (PT), Pb(Zr, Ti)O3 (PZT), and (Pb1−x, Lax) (Zry, Ti1−y)1−x/4O3 (PLZT) ceramic powders has been developed employing the acetate complexes of Pb2+, La3+, Zr4+, and Ti4+. The crystallization behavior (e.g., degree of crystallization and crystallite size) was examined over the temperature range of 400–700 °C with concentrations of excess lead varying from 0–5% using x-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy techniques. It was found that PT, PZT, and PLZT crystallize at temperatures as low as 450 °C, 500 °C, and 500 °C, respectively, and the excess lead required for crystallization of the perovskite phase is ⋚1%. Intermolecular mixing among acetate precursors via chelating and bridging structures was evident and appeared to be responsible for the low crystallization temperatures. The process is compared to the current sol-gel methods for its possible use in thin film ferroelectric manufacture.

On a formule un systeme de phosphatation/peinture en une seule etape comprenant un email polyester-melamine et H 3 PO 4 . On examine la stabilite du systeme, sa compatibilite, son durcissement thermique et les mecanismes chimiques qui interviennent, a l'aide de techniques experimentales et de modelisations.

A highly effective wetting agent and emulsifier, Triton X-100 detergent is introduced to metalorganic solutions. When applied to a substrate, this detergent/metalorganic solution promotes the formation of a uniform spin-on thin film with good adhesion. The precursor, copper formate film, was spin-deposited with a metalorganic solution prepared by a solvent mixture of methanol and Triton X-100 (50:1 by volume). KrF laser (248 nm) direct writing of high-purity copper patterns on glass and polyimide substrates has been achieved. When the laser beam is imaged through a slit device, periodic copper metal structures with a linewidth of ∼2.5 μm are observed, which may be attributed to result from Fraunhofer diffraction. A general process for casting homogeneous amorphous films on substrates from a solution of molecular or ionic metalorganics dissolved in the neutral or charged micelles is proposed.

— Steady-state and time-resolved emission spectroscopic techniques have been employed to characterize the drug species of dibucaine and to identify its location in micellar Triton X-100 (neutral), hexadecyltrimethyl ammonium bromide (cationic) and lithium dodecyl sulfate (anionic) solutions at 77 K. Under physiological conditions, the dibucaine is shown to exist in the free base form (D) while solubilized in the hydrocarbon core of neutral micelles. In cationic micellar solution, dibucaine exists as the monocation species (DH+) where the anesthetic is solubilized in the extramicellar aqueous solution and D is solubilized in the hydrophobic region with close proximity to the micellar interface. In the anionic micelles, interfacial solubilization is most consistent with a site in which the tertiary amine group of the monocation dibucaine (DH+) is anchored at the micellar interface with its quinoline analog penetrating the hydrophobic region. The distinct properties observed for the drug species (i. e. D and DH+) and their solubilization sites in micelles are consistent with a balance between hydrophobic forces, surface polarity and the interfacial electrostatic potential present in the micellar solubilization sites. These observations could lend insight into the molecular basis of pharmacological action, in particular the mechanism of local anesthetic drug transport across membranes.

Metal nanomaterials are shown to enhance gene expression for rice 𝛼 -galactosidase gene ( 𝛼 -Gal) in yeast cells. Au and Ag nanoparticles and their nanocomposites, silica-Au and silica-Ag, were prepared and characterized by UV-vis spectroscopy and TEM technique. The rice 𝛼 -galactosidase gene was cloned into the yeast chromosome, where the cloned cells were precultured and induced into a medium containing each of the testing nanomaterials. The nanomaterials were observed to incorporate inside the cells, and no cell death has been detected during the course of gene expression. The enzyme activity was determined by a synthetic substrate, p-nitrophenyl- 𝛼 -D-galctopyranoside, and the yellow product yield was recorded in a spectrophotometer at 400 nm. When Au and Ag nanoparticles were incorporated with the culture, a 3–5 fold enhancement in 𝛼 -galactosidase was observed for intracellular activity as well as the secreted activity into the medium. The secreted protein was analyzed to have a pure form and displayed as a single protein band in the SDS-gel electrophoresis. The effects of size and chemical nature of nanomaterials on gene expression for the rice 𝛼 -galactosidase gene in yeast cells are discussed.

Differential scanning calorimetry curves and circular dichroism spectra were determined for native bacteriorhodopsin (bR), deionized bR, acid blue and acid purple bR, 75% delipidated bR, deionized-delipidated bR and Mg2+ regenerated deionized bR. The effects of the different perturbations on the thermal stability (melting temperature) and the apparent helical content of the protein were examined. These perturbations have more influence on the deprotonation efficiency and the color change of retinal than on the thermal stability and the apparent helical content of the protein. Although the addition of Mg2+ to deionized bR restores the photochemical cycle, it does not restore the thermal stability to that of the native material.

Near infrared absorbing CsxWO3 nanoparticles with uniform particle size distribution were synthesized in two hours by solvothermal method. Benzyl alcohol was used as a main solvent and a reactant to facilitate a controlled reaction and stabilization in the presence of oleic acid as a capping agent. Different reaction conditions such as reaction time, reaction temperature, and oleic acid amount were studied and reported. Hexagonal CsxWO3 nanorods with average size of 80 nm were obtained in 2 h reaction time, at 240 °C reaction temperature, and 10% vol. oleic acid. Aqueous dispersion of the nanorods showed high transparency (about 80–90%) in visible light with strong near infrared (NIR) light shielding (80–90%). This indicates that CsxWO3 is an attractive material to employ in heat-shielding transparent coatings for windows of buildings and automobiles. Using this simple process, it is possible to synthesize homogenous CsxWO3 nanorods with low temperature and short reaction time. Moreover, the process offers an opportunity for large-scale synthesis of NIR absorbing nanorods.

Molecular complexes formed between a cooked food mutagen-carcinogen (2-amino-3-methylimidazo[4,5-f] quinoline, IQ) and a potent anti-mutagen (4-hydroxy-coumarin, 4HC) were synthesized and crystallized from a solution. The active functional groups in IQ and in 4HC that may involve in the formation of these complexes are investigated by UV–visible, infrared, and NMR spectroscopy. The geometrical conformations and heat of formation of IQ:4HC complexes were optimized by semi-empirical molecular orbital calculations. The experimental and theoretical results indicate that the complexes exist in multiple conformations. The energetically favorable ones are formed via hydrogen-bonding type of interactions between amino group in IQ and carbonyl group in 4HC, and also between quinoline-nitrogen (and imidazole-nitrogen) in IQ and hydroxyl group in 4HC. The observed complex formation could serve as a model for understanding the active molecular sites responsible for the initial mutagenic activity in cooked-food mutagens as well as the anti-mutagenic activity in coumarins.

The deposition by aqueous acetate solution (DAAS) technique has been developed for the preparation of 5% Fe-doped Pb(Zr/sub 0.53/Ti/sub 0.47/)O/sub 3/ (PZT) and (Pb/sub 0.93/La/sub 0.07/)(Zr/sub 0.65/Ti/sub 0.35/)/sub 0.983/O /sub 3/ (PLZT) thin films on Pt[111]/Ti/SiO/sub 2//Si substrates. PZT films, crystallized at 600 degrees C for 10 min, display good electrical properties and fatigue characteristics. Iron doping suppressed the crystallization of the films as measured by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. When 5% of the zirconium and titanium were replaced by iron in the stoichiometric precursor solution, the film crystallized predominantly in the [110] orientation. When 5% excess iron was added to the precursor solution, the film crystallized in the [100] orientation. The electronic states and charge species responsible for photoconductivity were investigated by emission/excitation and photocurrent action spectroscopy. The low photoemission at 77 K and high photoconductivity at 298 K in the doped thin films, as compared with thermally iron-doped ceramics, are attributed to surface energy quenching and low trapping state density. >

Magnetic perovskites of the general form La0.7Sr0.3Mn1−yFeyO3 (y = 0, 0.05, 0.10, and 0.15) have successfully been synthesized using deposition by aqueous acetate solution (DAAS). Crystalline, iron-doped, lanthanum strontium manganite (Fe-doped LSMO) powders are obtained by preparing an aqueous solution of metal acetate precursors in the proper stoichiometry, drying the solution to generate a glassy gel, consolidating the gel, and then firing the gel for short periods of time (0.7Sr0.3Mn1−yFeyO3 prepared by DAAS and annealed for 100 minutes at 1200°C are of high purity, are single phase, and exhibit excellent electrical and magnetic characteristics. Powders annealed at 1200°C or greater exhibit sharp metalinsulator transitions. Increasing the iron dopant concentration in these powders from 0% to 15% decreases the metal-insulator transition temperature of these samples from ∼360K to about 140K. The resistivity of these powders also increases with increasing substitution of the lattice B-site with iron, as does the unit cell volume of the lattice. Preparation of an iron doped LSMO powder that exhibits a maximum magnetoresistance at 305K was successfully carried out via a careful selection of iron content and anneal temperature. This compound, La0.7Sr0.3Mn0.93Fe0.07O3, exhibits a magnetoresistance of 40% at 305K and an applied field of 5 Tesla.

Magnetic perovskites of the general form La1-xSrxMnO3 have successfully been synthesized using deposition by aqueous acetate solution (DAAS). This novel technique, which has the potential for depositing large area min films with high throughput and low cost, involves the preparation of an aqueous metal acetate precursor solution, drying the solution to generate a glassy gel, consolidating the gel, and then firing it for short periods of time (0.83Sr0.17MnO3 annealed for 100 minutes at 1200°C were high purity, single phase, and exhibited excellent electrical and magnetic characteristics. Thin films of La0.7Sr0.17MnO3 deposited onto both sapphire and strontium titanate substrates and annealed at 900°C were also found to be crystalline, and substrate choice was found to influence thin film crystal structure. These films exhibited sharp metal-insulator transitions, and in the case of LSMO films on strontium titanate, magnetoresistance was observed at the unusually high temperature of ∼360K.

Photophysical properties of l-Docosyl-4-(4-hydroxystyryl)pyridiniurn bromide (SB), a merocyanine dye in solution and encapsulated in sol-gel derived glass are investigated at 298 and 77 K. In solution, the absorption spectra of SB display an equilibrium between the quinolinium and benzoid forms. The equilibrium can be shifted to either quinolinium or benzoid form under an acidic or basic condition, respectively. The emission spectra of SB, on the other hand, give not only the quinolinium and benzoid forms but also the quinoid form which emits at 500 nm. The existence of excited state quinoid form of SB is also evident in the excitation spectrum while the emission at 500 nm is monitored. Both in solution and in xerogel, the quinoid form of SB is shown to be photochemically unstable as compared to the benzoid form. It is proposed that the photoexcited quinolinium form of SB is a proton dissociative species which transforms readily to become the quinoid form. The results indicate that photochemistry channels of SB are originated from the quinoid form. Moreover, the benzoid form of SB (photochemically stable) exhibits large hyperpolarizability due to its charge-transfer characteristic, and is a desired molecular form for nonlinear optical (NLO) applications. The material processing techniques for stabilizing the benzoid form of SB in optically transparent sol-gel glasses are illustrated for the first time.

Deposition by aqueous acetate solution (DAAS) technique was used to synthesize undoped and 5 wt% Cr-, Mn-, Eu-, or Pr-doped Pb(Zr0.53Ti0.47O3 [PZT] thin films. The dopant was incorporated into PZT either in the precursor coating solution or via thermal diffusion into undoped PZT. X-ray diffraction shows that ion-doped PZT thin films on Pt/Ti/SiO2/Si (in particular, the Mn- and Eu- doped samples) display better crystallinity and smaller lattice parameters than those on sapphire substrates. The enhancement of photoconductivity at visible wavelengths measured by excitation photocurrent spectroscopy (EPS) goes as Cr-doped∼Mn-doped > Eu-doped ∼ Pr-doped. Only Mn-doped PZT perovskites have the band gap energy red-shifted to 360 nm from 330 nm. The space charge (or photovoltaic) field was estimated to be < 8 v when about 100 v was applied to ion-doped PZT thin films with 260 or 320 nm light. By using laser irradiation at selected wavelengths and switching the polarity of applied bias voltage, the expected changes in resistance (Ry) and remanent polarization (±Pr) states were observed in the P-E hysteresis loops. The possible applications of extrinsic ion-doped PZT thin films in optical memory devices are discussed.

Emission and excitation spectra for the local anesthetic drug, dibucaine.HCl in neutral and charged surfactant solutions and in bacteriorhodopsin (bR) have been investigated for lambda(ex) = 266 nm at room temperature. The total fluorescence and fluorescence anisotropy decays of the anesthetic in the same environments were also measured using a picosecond laser/streak camera system (lambda (ex = 266 nm)). The total fluorescence decay gave two components for dibucaine micellar and dibucaine bR solutions, one component in the range of 200-500 ps and the other in the range of 1200-3400 ps. Only the nanosecond timescale component was found for the dibucaine monomer surfactant solutions (1200-3000 ps), indicating that the anesthetic resides in the bulk solution. The fluorescence anisotropy decays of dibucaine in Triton X-100 and in lithium dodecyl sulfate (LDS) micelles are approximately 200 ps, which is attributed to dibucaine solubilized in the micellar environment. Dibucaine.HCl in anionic monomer solution exhibits an unusually large fluorescence anisotropy, r(t)max = 0.22 and a depolarization decay of less than 100 ps. This presumably results from a head-to-tail exciplex aggregation between the positively charged dibucaine and negatively charged dodecyl sulfate surfactant molecules. The anisotropy decay of dibucaine in bR is 300 ps. This solution was the only one which exhibited a residual fluorescence anisotropy, r(infinity) - 0.08. This implies that dibucaine is restricted in its rotational motion and suggests protein binding rather than lipid solubility.

— The emitting chromophores, emitting states, state orderings and phosphorescence lifetimes of neutral, hydrogen-bonded, and protonated dibucaines in water/alcohol mixtures were determined experimentally and were confirmed theoretically using a HAM/3 method. These photophysical properties are used to probe the deprotonation dynamics of dibucaine-HCl in the water/hydrophobic media. It is found that the protonated dibucaine in an aqueous solution is deprotonated and/or forms hydrogen-bonded dibucaine when it is brought into contact with the alcohols and surfactants. The observed deprotonation processes could lend some insight on the molecular basis of pharmacological action of dibucaine.

The presence of a biphasic circular dichroism (CD) observed in the visible absorption spectrum of retinal in bacteriorhodopsin (bR) has been believed for many years to be due to excitonic-type interaction within the trimeric structure of the retinal in the protein membrane. In the present work, we present data and discuss previous observations that strongly suggest the absence of such an excitonic interaction. The magnetic CD spectrum of the trimer is found to be similar to that of the monomer and shows no sign of absorption to the doubly degenerate state predicted to be present from the exciton theory. This, together with the previous observations on the CD spectra of the photocycle intermediates of bR as well as the linear polarization studies of the fluorescence and the daughter absorption, sheds doubt on the presence of exciton interaction and thus suggests the presence of neither an antenna system nor a viable special reaction center in bR. Possible explanation for the observed biphasic nature of the CD spectrum is given in terms of having more than one type of bR with different protein conformations around the retinals in the trimer giving each similar absorption maximum but opposite signs for its rotary dispersion power.

Six 2′-hydroxychalcone derivatives with a methyl group on the α-position were synthesized. Infrared absorption spectra of these new compounds are discussed taking their corresponding α-hydrogen chalcoes which were also synthesized for comparison. This latter study is also utilized as a proof for the structures of these compounds of a new series.