Engineering FeS2 nanoparticles on tubular g-C3N4 for photo-Fenton treatment of paint wastewater

An efficient photo-Fenton catalyst （Fe S₂@HTCN） was designed by maximizing the synergistic effect of Fe S₂nanoparticles and hollow tubular g-C₃N₄（HTCN）.Molecule self-assembly and molten salts-assisted calcination were used to engineering the hollow structured g-C₃N₄before anchoring Fe S₂nanoparticles on the walls of HTCN via reflux method.Compared to bulk g-C₃N₄,the unique structure of HTCN and het...     

Permeability of polymer materials to compounds containing radionuclides

The permeability of rubber and PE gloves, PE bags and strippable PVC paint to HTO, Na¹²⁵I, H₂ ³⁵SO₄, H₃ ³²PO₄,¹⁴¹CeCl₃,⁸⁹SrCl₂, and,¹³⁷CsCl in aqueous solution was tested. All materials were permeable to HTO and Na¹²⁵I. Whereas rubber gloves were permeable the other materials were impermeable to H₂ ³⁵SO₄. The remaining radioactive compounds showed no penetration. The diffusion coefficients of the penetrating compounds were calculated on the basis of Fick's First Law for the respective materials. The permeability to Na¹²⁵I and HTO decreases in the order rubber, PVC paint, and PE. Penetration increases in the order H₂ ³⁵SO₄, Na¹²⁵I, and HTO.     

Chemical discrimination of multilayered paint cross sections for potential forensic applications using time‐of‐flight secondary ion mass spectrometry

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) equipped with a bismuth imaging source and an argon gas cluster ion beam (GCIB) was used to image polished cross‐sections of four automotive multilayer paint samples. Secondary ion mass spectrometry chemical imaging of the individual layers was possible after a GCIB sputter ion dose of (7 × 10¹⁵) ions/cm² was applied for the removal of polishing residue, at which point the chemical composition of the individual clear coats could be distinguished using principal components analysis. For the differentiation of the four clear coat chemistries, only four secondary ion peaks were necessary; C₂H₅O⁺ (m/z 45.04), C₉H₉NO₂⁺ (m/z 163.09), and C₁₀H₁₁NO₂⁺ (m/z 177.10) that appeared to be fragments of the carbamate‐based clear coat, and C₇H₁₁⁺ (m/z 95.09) that was strongly associated with the polyurethane‐based clear coat. Clear identification of the four paint samples based on this short peak list highlights the strength of the SIMS technique as a potential forensic approach to discriminate automotive paints and suggests that many more variables could be included in the multivariate and statistical analysis to differentiate a wider range of clear coat chemistries.     

Electron energy loss spectroscopy elucidates the elusive darkening of zinc potassium chromate in Georges Seurat’s <Emphasis Type="BoldItalic">A Sunday on La Grande Jatte—1884</Emphasis>

The color darkening of selected brushstrokes of Georges Seurat’s A Sunday on La Grande Jatte—1884 was noted as early as 1892. Artificial aging of model systems containing zinc yellow (K₂O·4ZnCrO₄·3H₂O) mixed with linseed oil successfully replicated the phenomena observed on La Grande Jatte. Electron energy loss spectroscopy measurements performed on the uppermost few microns of thin sections of the paint layers (obtained with focused ion beam milling) determined that samples which turned olive green (aged at 90% RH, with SO₂ and light) contain mostly the altered species Cr(III) and that the ochre-yellow coloration of specimens aged at 50% RH with SO₂ and light is due to the presence of dichromate ions (Cr (VI)). The altered species are only present in the first few microns of paint and are likely poorly crystalline, so that they eluded other types of bulk and surface measurements, but they create a substantial color alteration at the surface of the paint films. A similar phenomenon was confirmed on a sample from La Grande Jatte, where Cr(III) and Cr(VI) dichromate ions were detected in the ochre-colored, altered brushstrokes of zinc yellow. Laboratory simulations demonstrated that the equilibrium between chromate and dichromate ions is reversible within the paint film and that the orange dichromate ions can be transformed back into bright yellow chromates by exposure to highly alkaline gases.     

Bi-Enzyme Alcohol Biosensors Based on Genetically Engineered Alcohol Oxidase and Different Peroxidases

We report on the development of a bi-layer bi-enzyme biosensor architecture using different peroxidases and alcohol oxidase from Hansenula polymorpha C-105 as biological recognition elements. The sensor architecture comprises a first layer containing either horseradish peroxidase or royal palm tree peroxidase crosslinked with an Osmium complex-modified redox hydrogel. On top, a second layer was formed by electrochemically induced precipitation of a cathodic electrodeposition paint simultaneously entrapping alcohol oxidase isolated from a genetically modified strain of Hansenula polymorpha C-105. The sensor architecture was optimized with respect to effective electron transfer and stability of the enzyme. The main characteristics of the biosensors are an apparent maximal current I_max^app of 572–940 nA, an apparent Michaelis constant K_M^app of 9.5 mM, a sensitivity of 60–98 nA mM⁻¹ and an improved operational stability represented by a deactivation constant of 1.5–2.0 × 10⁻⁴min⁻¹.     

Synthesis of polyaniline and application in the design of formulations of conductive paints

Polyaniline (PANI) is prepared by chemical polymerization of aniline in acidic medium using ammonium peroxydisulfate ((NH₄)₂S₂O₈) as oxidant. The polymer, with a conductivity of 25–30 S/cm, is used to formulate conducting paints. A stable paint with a conductivity of 10^?3 S/cm is obtained. Copyright © 2004 John Wiley & Sons, Ltd.     

14C dating of ancient rock art: A new application of plasma chemistry

We have developed a new statically operated oxygen plasma method that allows direct¹⁴C dates to be obtained from ancient rock paintings. The method is applicable even to paintings on limestone (CaCO₃) walls. A sample of a pictograph which had naturally spalled offa shelter wall in the Lower Pecos region of Texas was subjected to a low temperature ( 150°C) oxygen plasma to selectively remove the organic carbon-containing material used in the paint as CO₂, without contamination from the limestone substrate. The Zürich EHT accelerator mass spectrometer was then used to determine the radiocarbon age of this prehistoric rock painting. It was successfully dated at 3865 ± 100 years BP, in good accord with the archaeological context which has set the onset of this Pecos River style of pictograph between 4100 and 3200 years BP. The method appears feasible and is applicable to rock art in which organic materials were used in the paint.     

Unraveling the Composition of Rembrandt's Impasto through the Identification of Unusual Plumbonacrite by Multimodal X‐ray Diffraction Analysis

Rembrandt (1606–1669) is renowned for his impasto technique, involving his use of lead white paint with outstanding rheological properties. This paint was obtained by combining lead white pigment (a mixture of cerussite PbCO₃ and hydrocerussite Pb₃(CO₃)₂(OH)₂) with an organic binding medium, but the exact formulation used by Rembrandt remains a mystery. A powerful combination of high‐angle and high‐lateral resolution x‐ray diffraction was used to investigate several microscopic paint samples from four Rembrandt masterpieces. A rare lead compound, plumbonacrite (Pb₅(CO₃)₃O(OH)₂), was detected in areas of impasto. This can be considered a fingerprint of Rembrandt's recipe and is evidence of the use of an alkaline binding medium, which sheds a new light on Rembrandt's pictorial technique.     

Sensitive Determination of Lead by Flame Atomic Absorption Spectrometry Improved with Branched Capillary as Hydride Generator and Without Phase Separation

The sensitivity of traditional flame atomic absorption spectrometry (FAAS) is low for the determination of lead. Therefore, a simple branched capillary was used for hydride generation with air-acetylene FAAS determination of lead in geochemical samples and paint. Using a Y-shaped connector, the sampling capillary of a traditional FAAS instrument was branched, with one branch for introducing the reductant solution, KBH₄, and the other for the sample solution, Pb⁴⁺. The KBH₄ solution and the Pb⁴⁺ solution were then merged and mixed inside the reaction capillary and thereafter inside the nebulizer for generating the lead hydride, which, together with the liquid fine droplets, was directly brought into the air-acetylene flame for atomization without gas/liquid separation. The experimental conditions were optimized for best signal-to-noise ratio (S/N). A calibration curve was obtained with a linear dynamic range of up to 1.0 mg L⁻¹ and a correlation coefficient of 0.9997. The limit of detection (LOD) for lead was found to be 0.004 mg L⁻¹, 10 times better than that of traditional FAAS and slightly better than or equivalent to that of the sophisticated inductively coupled plasma atomic emission spectrometry (ICP-AES). The improvement in sensitivity and the LOD for lead largely owe to the altered atomization mechanism via hydride generation. The proposed method was successfully applied to the determination of lead in Geochemical Standard Deposit (GSD) samples and paint samples.     

Preparation,thermal, XRD,chemical and FTIR spectral analysis of NiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles and respective precursor

Samples of water based commercial acrylic resin paints were spread in a film form on slides, dried at room temperature and exposed to solar radiation for up to eight months. The characterization and quantification of resins and charges in the white paint emulsion were carried out for the thermal decomposition. Besides this, X-ray diffractometry was used to identify CaCO₃ as charge and TiO₂ (rutile phase) as pigment. It was observed through thermal techniques similar behavior to the samples even though with varied exposure time. Kinetic studies of the samples allowed to obtain the activation energy (E _a) and Arrhenius parameters (A) to the thermal decomposition of acrylic resin to three different commercial emulsion (called P₁, P₂, P₃) through non-isothermal procedures. The values of E _a varied regarding the exposition time (eight months) and solar radiation from 173 to 197 kJ mol⁻¹ (P₁ sample), from 175 to 226 kJ mol⁻¹ (P₂ sample) and 206 to 197 kJ mol⁻¹ (P₃ sample). Kinetic Compensation Effect (KCE) observed for samples P₂ and P₃ indicate acrylic resin s present in these may be similar in nature. This aspect could be observed by a small difference in the thermal behavior of the TG curves from P₁ to P₂ and P₃ sample. The simulated kinetic model to all the samples was the autocatalytic Šesták-Berggreen.     

Plumbonacrite Identified by X‐ray Powder Diffraction Tomography as a Missing Link during Degradation of Red Lead in a Van Gogh Painting

Red lead, a semiconductor pigment used by artists since antiquity, is known to undergo several discoloration phenomena. These transformations are either described as darkening of the pigment caused by the formation of either plattnerite (β‐PbO₂) or galena (PbS) or as whitening by which red lead is converted into anglesite (PbSO₄) or (hydro)cerussite (2 PbCO₃?Pb(OH)₂; PbCO₃). X‐ray powder diffraction tomography, a powerful analytical method that allows visualization of the internal distribution of different crystalline compounds in complex samples, was used to investigate a microscopic paint sample from a Van Gogh painting. A very rare lead mineral, plumbonacrite (3 PbCO₃? Pb(OH)₂?PbO), was revealed to be present. This is the first reported occurrence of this compound in a painting dating from before the mid 20th century. It constitutes the missing link between on the one hand the photoinduced reduction of red lead and on the other hand (hydro)cerussite, and thus sheds new light on the whitening of red lead.     

Localization of proteins in paint cross-sections by scanning electrochemical microscopy as an alternative immunochemical detection technique

The qualitative identification of proteinaceous substances, as well as their location within a complex paint stratigraphy, is one of the most challenging issues in the characterization of painting materials. Nevertheless, information on paint components represent a crucial task for studies concerning both the ancient painting techniques adopted and the state of conservation, being fundamental investigations for the selection of appropriate conservation actions. The present research was aimed at developing a new detection approach for the immunochemical localization of ovalbumin in paint cross-sections based on the use of scanning electrochemical microscopy (SECM). The immunochemical analyses were performed using an anti-ovalbumin primary antibody and a secondary antibody labelled with horseradish peroxidase (HRP). SECM measurements were performed in feedback mode using benzoquinone (BQ)/hydroquinone (H₂Q) redox couple. In presence of hydrogen peroxide (H₂O₂), HRP catalyzes the re-oxidation of H₂Q to BQ and the increment of BQ concentration in correspondence of the target protein was detected by SECM through the electrochemical reduction of the regenerated BQ at the microelectrode. Indeed, the localization of ovalbumin was possible thanks to a clear discrimination of SECM currents, achieved by the comparison of the measurements recorded before and after H₂O₂ administration, based on the HRP on/off approach. The method was evaluated both on samples from standard mocks-up and on a historical sample, collected from a Renaissance wood painting. The obtained results were promising, foreseeing a wider application of SECM on cultural heritage researches.     

Influence of paint components on photoactivity of P25 titania toward NO abatement

The present work studies the interference of paint components on the photoactivity of P25 photocatalyst toward NO abatement. Paint components are divided in two major groups: powder inorganic components and organic components. Two types of films were prepared, powder pressed films and films made of pseudo-paints, and their photoactivity assessed following approximately standard ISO 22197-1:2007(E). Powder pressed films were obtained by stepwise mixing powder components of the base paint; pseudo-paint films involved mixing the powder components stepwise with families of organic components present in the original photocatalytic paint formulation.It was concluded that the morphology of powder pressed films influences the photoactivity while CaCO₃ and silicates, which are extenders, have a smaller impact on P25 photoactivity compared to pigmentary TiO₂.Pseudo-paint films containing the same proportion of powder components as powder pressed films displayed different transient behaviors but similar steady-state photo-activities, regardless the presence of organic components such as the binder. This was assigned to the photo-erosion of a significant fraction of the organic paint components during the transient period. Therefore, after reaching steady-state, NO photooxidation could proceed freely as if only inorganic paint components were present. An average of ca. 25 wt.% of organic phase erosion was observed but more severe erosion should occur closer to the top of the paint film.     

Poly(vinyl acetate) paints in works of art: A photochemical approach. Part 1

The photochemistry of poly(vinyl acetate), PVAc, homopolymer, of PVAc mixtures with selected pigments and fillers, and of accurate historic reproductions based on the colours prepared by Portuguese artist Joaquim Rodrigo and on those supplied by the company A Favrel was studied. The systems, applied as films, were irradiated at λ ≥ 300 nm and the changes followed by size exclusion chromatography, infrared spectroscopy, and colorimetry.PVAc as homopolymer or as an emulsion paint proved to be very stable to light, and after 5000 h of irradiation no gel fraction was observed. Φ_R (λ_irr = 313 nm) for chain scission for PVAc was determined to be 7 × 10⁻⁸. This value indicates that the mechanism/s operating when irradiating at λ ≥ 300 nm are different from those previously published with irradiation involving 254 nm. No side-group scission was observed, and main chain scission is the foremost photodegradation mechanism. Also, the metal ions present in the pigments do not affect the photochemical stability of the polymer.     

Polarographic studies on tributyltin oxide in dichloromethane and tetrahydrofuran with application to antifouling paint

In the presence of tributyltin oxide, (Bu₃Sn)₂O, an oxidation process is observed at mercury electrodes in non-aqueous solvents. On the polarographic time-scale, the oxidation involves the mercury electrode and is believed to occur according to the following reaction scheme: 2Bu₃SnOSnBu₃ + 2Hg?[Bu₃SnHgSnBu₃]²⁺ + Hg (OSnBu₃)₂ + 2e^? Hg(OSnBu₃)₂+2Hg?[BuSnHgSnBu₃]²⁺ + 2HgO+2e^? to give the overall process Bu₃SnOSnBu₃+2Hg?[Bu₃SnHgSnBu₃]²⁺ + HgO+2e^?. On the time scale of controlled-potential electrolysis, [Bu₃SnHgSnBu₃]²⁺ is unstable and additional electron transfer occurs. The oxidation process forms the basis of a specific high-performance liquid chromatographic method for the determination of tributylin oxide in antifouling paint. A static mercury drop electrode in the hanging drop mode is used as an amperometric detector in a flow-cell configuration.     

掺铒联吡啶钌为探针分子压敏漆的制备及氧猝灭特性

以2,2′-联吡啶,三氯化钌(RuCl3),氯化铒(ErCl3)为原料合成了铒掺杂的探针分子。将探针分子加入到铕掺杂的硅溶胶基质中获得了铕、铒共掺杂的压敏漆样品。采用IR,SEM,EDS及荧光发射光谱对探针分子和压敏漆进行了表征。红外光谱结果表明,探针分子中联吡啶的结构没有被破坏。扫描电镜观察发现探针分子呈片状,EDS测试发现探针分子表面含有Er,Ru等元素。紫外吸收光谱表明压敏漆的最佳吸收波段位于200~500 nm处,选择410 nm作为激发光源,压敏漆在590 nm处有很强的荧光发射,并且随着空气压力的增大(即氧分子浓度的增加),压敏漆的荧光发射强度降低,说明压敏漆具有较好的氧猝灭特性。     

Low-temperature combustion synthesis of CuCr2O4 spinel powder for spectrally selective paints

CuCr₂O₄ spinel powder with high quality black hue, investigated as solar-absorbing pigment for spectrally selective paint, was synthesized by an environmental friendly sol–gel combustion process using citric acid as the fuel and metal nitrates as oxidizers. Single-phase CuCr₂O₄ spinel crystals were obtained after heat treatment of the as-burnt powder at a low temperature (600 °C) and the average crystallite size of the CuCr₂O₄ powders increased with the calcining temperature. Morphological analysis of powders calcined at various temperatures was done by field emission scanning electron microscopy. CuCr₂O₄ powder calcined at 700 °C was chosen as pigment to fabricate thickness sensitive spectrally selective paint coatings by simple spray-coating technique. For the sake of comparison, the as-burnt powder composed of mixed metal oxides (i.e., CuO and Cr₂O₃) was also used as pigment. The results reveal that the spinel CuCr₂O₄ based paint coatings exhibit much higher spectral selectivity (α _s = 0.88–0.91, ε ₁₀₀ = 0.27–0.35) which is depending on the coating thicknesses than that of coatings using as-burnt powder as pigment (α _s = 0.83–0.88, ε ₁₀₀ = 0.60–0.66). The CuCr₂O₄-based paint coatings showed no visible degradation after 600 h of condensation test and the performance criterion value is 0.04, indicating that the coatings have excellent long term stability.     

Activation and properties of Mo=O bonds in Mo/SiO2 catalysts

The existence of the charge transfer excited triplet state [Mo⁵⁺-O^-] produced by UV-irradiation of Mo/SiO₂ catalysts, and its reactivity are evidenced by experiments of photoluminescence, photoinduced metathesis, and photoreduction of CO. Mo⁵⁺ ions can be produced separately by thermal activation and O^- ions by further adsorption of N₂O on those Mo⁵⁺ ions. The latter of which are adsorbed on Mo⁶⁺ ions are found to be more reactive than O^2- of [Mo⁶⁺ =O^2-] bond. They are able either to add a molecule such as CO or C₂H₄, or to abstract hydrogen from H₂, CH₄ or trans-dicyanoethylene, or a CN group form tetracyanoethylene (TCNE). The Mo⁵⁺ ions are able to coordinate gas phase ligands when their coordination sphere possesses vacant sites. This is the case for tetracoordinated Mo⁵⁺ _4c ions arising from reduction of tetrahedral Mo⁶⁺ ions (Eq. (7)). These Mo⁵⁺ _4c ions are similar to those produced by UV-irradiaiion (Eq. (2)). In addition, if the adsorbed molecule has a sufficiently large electron affinity, such as TCNE or O₂, an electron transfer can occur (Eq. (9) and (17)). The [Mo⁵⁺-O^-] bond obtained by thermal activation is more difficult to evidence than that obtained with UV-activation because it is not detectable by EPR. However, the EPR results obtained at low temperature show that the O^- ions adsorbed on Mo/SiO₂ catalysts as well as the [Mo⁵⁺-O^-] excited triplet state obtained by UV-irradiation of 1Mo⁶⁺=O²] interact with methanol (Eq. (16)). They are consistent with the mechanism of methanol oxidation occurring at high temperature (Eq. (4)).     

Controllable Coordination Self‐Assembly Based on Flexible Tripodal Ligands: From Finite Metallocages to Infinite Polycatenanes Step by Step

This article describes the developments in coordination self‐assembly based on flexible tripodal ligands with different metal species. Various finite metallocages such as M₃L₂, M₆L₈, M₆L₄, M₄L₄ and different catenanes based on discrete metallocages constructed from flexible tripodal ligands with suitable metal species are presented here. Many M₃L₂ metallocages based on ligands L¹–L¹² and different two‐coordinated metal species have been prepared, in which various Ag(I) salts and other metal species that have been protected by suitable groups, such as Zn(OAc)₂, ZnBr₂, and PdBr₂, have been used as effective acceptors. All of the M₆L₈‐type metallocages are constructed from ligands L² or L¹²–L²⁰ and different four‐coordinated metal species, such as various palladium(II) salts or NiCl₂, and have similar topological structures. Only a few discrete M₆L₄‐type metallocages, based on ligands L²¹–L²⁴, have been reported, using different strategies such as protecting groups and steric hindrance. All of the M₄L₄‐type cages have similar topological structures and are constructed from ligands L²⁵–L²⁹ with multiple donor sites. More intriguing interlocking ensembles constructed from discrete metallocages are also described here in detail, namely, three [2]catenanes based on ligands L³⁰–L³² and four polycatenanes based on ligands L³³–L³⁴.     

Application of non-isothermal cure kinetics on the interaction of poly(ethylene terephthalate) — Alkyd resin paints

Samples of paint (P), reused PET (PET-R) and paint/PET-R mixtures (PPET-R) were evaluated using DSC to verify their physical-chemical properties and thermal behavior. Films from paints and PPET-R are visually similar. It was possible to establish that the maximum amount of PET-R that can be added to paint without significantly altering its filming properties is 2%. The cure process (80–203°C) was identified through DSC curves. The kinetic parameters, activation energy (E _a) and Arrhenius parameters (A) for the samples containing 0.5 to 1% of PET-R, were calculated using the Flynn-Wall-Ozawa isoconversional method. It was observed that for greater amounts of PET-R added, there is a decrease in the E _a values for the cure process. A Kinetic compensation effect (KCE), represented by the equation InA=−2.70+0.31E _a was observed for all the samples. The most suitable kinetic model to describe this cure process is the autocatalytic Šesták-Berggreen, model applied to heterogeneous systems.