Ammonium Hexachloroplatinate Research Articles

Statistical investigation of the experimental variables in the hydrosilylation reaction of a trimethylsiloxy‐terminated poly (methylhydro‐dimethyl)siloxane copolymer and an unsaturated polyethylene glycol using response surface methodology

The hydrosilylation reaction is a suitable route to prepare efficient, transparent, and low‐viscose silicone surfactants with low surface tension. Initial materials, the catalyst used, and experimental conditions are highly effective variables to achieve the maximum efficiency of the reaction, reduce the consumption of the catalyst, and prevent side reactions. To draw a comprehensive conclusion on the effect of these variables, a series of trimethylsiloxy‐terminated poly (methylhydro‐dimethyl)siloxanes copolymer (abbreviated as RSiH with different preceding numbers) and two unsaturated polyethylene glycols (UPEG200 and UPEG400) were selected, and the reactions in the presence of two platinum‐based catalysts, namely, hexachloroplatinic acid and ammonium hexachloroplatinate, were statistically studied by Design of Experiment. After initial pre‐investigations, the amounts of reactant and catalyst were subjected to analysis of variance using response surface methodology (RSM). Based on the results, low‐viscose and low‐surface tension silicone surfactants were obtained using UPEG400, RSiH105, and (NH4)2PtCl6 as catalysts, at temperatures over 170 °C. The best results were obtained with a relatively low concentration of the catalyst between 2.57 × 10−6 and 2.72 × 10−6 equivalent catalyst per UPEG. The relative equivalent ratio of [UPEG]/[RSiH] at the optimum condition was 1.6, which provided a surface tension below 21 mN/m together with a minimum amount of unreacted RSiH (less than 3%). The silicone surfactant was characterized as a pure product by a series of spectroscopic methods, such as FT‐IR and 1H NMR spectroscopies, as well as bromine number index. These excellent properties make this compound a new alternative in various industries.

Application of cupric or ferric ions as environmentally benign oxidants to the chloride leaching of platinum from spent reforming catalysts

Recovery of precious metals has been considered due to their limited availability and resources, and the reduction of environmental hazards. In this study, the environmentally friendly chloride leaching method was used to recover platinum (Pt) from a spent reforming catalyst. Hydrochloric acid and sodium chloride were applied as the complexing agent and ferric or cupric chloride (FeCl3, CuCl2) was used as oxidants. Response surface methodology was implemented to investigate the influences of acid concentration (1–3 M), oxidant concentration (0.5–1.3 M), and temperature (70–90 °C) on the Pt extraction at a fixed duration of 3 h using two separate Box-Behnken experimental designs. Increasing temperature and acid concentration improved the Pt recovery from ∼52% to ∼89% in the presence of 1 M FeCl3, and from ∼29% to 94% in the presence of 0.75 M CuCl2. Generally, at low acid concentrations, ferric chloride was more efficient in Pt dissolution, while, at high acid concentrations, cupric chloride performed better. Finally, the platinum content of the pregnant leach solution was precipitated by adding a saturated ammonium chloride solution. According to the results of the X-ray diffraction analysis, the obtained precipitate was mainly composed of ammonium hexachloroplatinate, sodium chloride, and ammonium chloride. Also, the Pt assay of the powder was determined as 21%.

A new cytometry-based method reveals an accumulation of Nrf2 in dendritic cells exposed to two respiratory sensitizers.

The mechanisms underlying chemical respiratory sensitization are incompletely understood. One of the major cell types involved in this pathology are dendritic cells. In this study, the mechanisms of the NRF2-Keap1 pathway were studied using a bone marrow-derived dendritic cell model exposed to two respiratory sensitizers: ammonium hexachloroplatinate (HCP) and ammonium tetrachloroplatinate (ATCP). Expression levels for two Nrf2-regulated genes, hmox1 and srxn1, were analyzed by real time-quantitative polymerase chain reaction. A flow cytometry-based method was also developed to measure intracellular Nrf2 accumulation in dendritic cells following exposure. Exposure to HCP and ATCP increased both hmox1 and srxn1 gene expression, and was associated with accumulation of Nrf2 protein in cells. Overall, these results show that the respiratory sensitizers, in addition to skin sensitizers, can also induced markers associated with NRF2-Keap1 pathway activation in dendritic cells. This study contributes to a better understanding of the adverse outcome of respiratory sensitization.

Time-resolved study of thermal decomposition process of (NH4)2[PtCl6]: Intermediates and Pt nucleation

Evolution in crystal, electronic and local atomic structures of Pt in ammonium hexachloroplatinate in the course of thermal decomposition in inert and reducing atmospheres have been studied by Powder X-Ray Diffraction (PXRD) and Quick X-ray Absorption Fine Structure (QXAFS) at Pt L3-edge for deeper understanding the thermally-induced solid state reaction and the formation of metallic nanoparticles. A three-step thermal decomposition mechanism of (NH4)2[PtCl6] in the inert atmosphere with the intermediate products Pt(NH3)2Cl2 and PtCl2 has been found instead one-[G.Meyer, A.Möller, J. Less. Common. Met. 170 (1991) 327–331] and two-step one [Q.Kong, F.Baudelet, J.Han, S.Chagnot, L.Barthe, J.Headspith, R. Goldsbrough, F.E.Picca, O.Spalla, Sci. Rep. 2 (2012) 1018–1025] considered early. In the reducing atmosphere, the thermal decomposition is a two-step process with the formation of the intermediate PtCl2. The best approach to determining the number of thermal decomposition steps turned out to be the express-analysis of QXAFS spectra offered in the papers, based on the simultaneous presentation of the most important parameters extracted from X-ray Absorption Near Edge Structure (XANES) and Fourier transformed Extended XAFS (EXAFS). This express-analysis was tested by comparison with results of various approaches such as conventional EXAFS fitting, linear combination fit (LCF), Multivariate Curve Resolution Alternating Least Squares method (MCR ALS).

Synthesis of a Pt/C Electrocatalyst from a User-Friendly Pt Precursor (Ammonium Hexachloroplatinate) through Microwave-Assisted Polyol Synthesis

Ammonium hexachloroplatinate (NH4)2PtCl6, owing to its low solubility in NH4Cl-containing aqueous solutions, is an intermediate compound during the hydrometallurgical extraction of platinum. As a r...

Morphology-Controlled Pt Alloy Nanoparticles for Oxygen Reduction Reaction

Proton-exchange membrane (PEM) fuel cell, which can provide clean electricity with high efficiency, is essential for improving the sustainability of our society. Since oxygen reduction reaction (ORR) limits the performance of PEM fuel cells, precious platinum catalyst is crucial in the cathode electrode. Recently, Pt and its alloy nanoparticles (NPs) with controlled morphology have been attracted to reduce the amount of Pt loading. For example, nano-frames, nao-rods, nano-plates, etc. have been reported. As reduction rate and/or stability of a chemical reaction from ionic to metallic state play a key role to synthesize morphology-controlled NPs, in 233rd ECS meeting, we have shown a control technique of oxidation-reduction potential (ORP). However, the controllable range of ORP was revealed to be narrow, which suggests that controllability of the reduction rate needs to be extended. In order to delay the reduction rate for morphology control of Pt alloy NPs, solid precursor instead of ionic counterpart is hopeful. Herein, ammonium hexachloroplatinate which is generated in recycling process is chosen as Pt precursor. The ammonium hexachloroplatinate hardly dissolves in aqueous ammonium chloride solution, whereas it is known to dissolve well in water. In the present work, we demonstrate a facile synthesis method of morphology-controlled Pt alloy NPs by using solid Pt precursor. The ammonium hexachloroplatinate was chemically reduced with Cu ions on carbon support. Synthetic solution was adjusted to be water or ammonium chloride solution, and the samples were labelled as without-NH4Cl and with-NH4Cl, respectively. Transmission electron microscope (TEM) observation revealed that, in the without-NH4Cl, highly dispersed small NPs were deposited on carbon support. On the other hand, in the with-NH4Cl, catalytic NPs were obviously larger than those in the without-NH4Cl, and the morphology was not spherical but plate-like. X-ray diffraction (XRD) profiles indicated that crystal phases of both samples were mainly composed of Pt-Cu alloy crystal. ORR catalytic activities were measured for the small Pt alloy NPs (without-NH4Cl), the plate-like Pt alloy NPs (with-NH4Cl) and commercial Pt. Compared to the commercial Pt, electrochemical active surface area (ECSA) of the without-NH4Cl was almost the same and that of the with-NH4Cl was relatively smaller. This hierarchy is corresponding to particle diameters obtained by the TEM observation. Mass activities of our samples were higher than the commercial Pt, especially, the without-NH4Cl showed a 2-fold increase. The with-NH4Cl exhibited 4 times higher specific activity. Therefore, plate-like Pt alloy NPs will achieve drastically higher mass activity if ECSA is improved. In order to explain the ORR catalytic activities of the synthetic samples, a model of structure of the catalytic NPs was constructed (see Figure). The with-NH4Cl has larger diameter of the catalytic NPs, which indicates more atoms are located at the core of the particles. Since Pt atoms at the core are catalytically inactive, with-NH4Cl showed smaller ECSA than the without-NH4Cl. However, at the same time, the without-NH4Cl has more Cu atoms at the surface, and exposed Cu atoms are easy to leach out during potential scans in acidic solution. In Pt alloy catalysts, transition metals including Cu exhibit an important synergistic effect. When Cu atoms combine with Pt atoms, electronic state of surface Pt changes and surface adsorption energy is tuned, which contributes to an enhancement of ORR catalytic activity. As a result, with-NH4Cl which has larger diameter inhibited leaching of Cu atoms at the core, and sustained the synergistic effect to enhance specific activity. Moreover, plate-like morphology of the with-NH4Cl can be another factor of the high specific activity by selective exposure of active facet. It is reported that Pt nano-plates selectively expose active facet and exhibit high specific activity. In conclusion, we adjusted concentration of ammonium chloride in aqueous synthetic solution to control reduction rate of Pt and morphology of Pt alloy NPs supported on carbon. Highly dispersed small Pt alloy NPs were synthesized in water, whereas plate-like Pt alloy NPs which showed high specific activity were synthesized in aqueous ammonium chloride solution. However, when the concentration of ammonium chloride is excess, the chemical reduction of Pt is inhibited and synthetic yield decreases. Thus, the addition amount of ammonium chloride requires careful consideration. Figure 1

Pt/C Electrocatalyst Synthesis from Recycling of the Spent PEMFC Membrane Electrode Assembly: A Closed Loop Circular Economy

Large-scale commercialization and sustainable growth of proton exchange membrane fuel cells (PEMFCs) technology depends largely on availability of the raw materials. Here, technical details of a closed loop recycling of spent electrocatalyst from a PEMFC electrode is demonstrated. The process includes electrochemical dissolution of the Pt nanoparticles in dilute acidic bath, precipitation of the dissolved Pt in form of a Pt-salt and synthesis of carbon supported Pt (Pt/C) electrocatalyst through reduction of the Pt-salt. Spent electrocatalysts from PEMFC electrodes, owing to their high activity, were subjected to dissolution through potentiodynamic treatment in dilute (0.1 M or 1 M) HCl bath to attain a Pt concentration of ∼0.7 mg/mL. Pt was recovered from the electrolyte by precipitation in form of ammonium hexachloroplatinate, which was converted to Pt/C electrocatalyst (20 wt% Pt) through reduction by refluxing in an ethylene glycol/water (1:1 v/v) mixture. Electrochemical surface area measurement and accelerated stress test of the synthesized Pt/C exhibit performances similar to or better than that of commercial Pt/C (20 wt% Pt). With a demonstrated recovery efficiency >90%, the process may be utilized for large-scale recycling of the spent electrocatalysts, especially suitable for PEMFC electrodes.

Cross-reactivity between halogenated platinum salts in an immediate-type respiratory hypersensitivity model

Halogenated platinum salts can trigger the development of occupational asthma. Until recently, laboratory research into the development and manifestation of platinum hypersensitivity responses were hindered by the lack of an animal model suitable for assessing the functional consequences of allergic sensitization. We employed a newly developed mouse model to assess the potential allergenicity of ammonium tetrachloroplatinate (ATCP), compare the relative potency of ATCP and another platinum salt, ammonium hexachloroplatinate (AHCP) and assess potential cross-reactivity. Mice were topically sensitized with ATCP before being challenged by intratracheal aspiration (IA) with ATCP. Ventilatory responses were assessed using whole-body plethysmography (WBP). An immediate response (IR) was observed in ATCP-sensitized and challenged mice. Two days later, responsiveness to the nonspecific stimuli methacholine (Mch) was detected in ATCP-sensitized mice using WBP. Bronchoalveolar lavage fluid collected from sensitized mice contained an average of 3.3% eosinophils compared to less than 0.5% in non-sensitized mice (p<.05). Serum harvested from sensitized mice also contained increased total serum immunoglobulin E (p<.05). These data are the first to demonstrate that topical exposure to ATCP is sufficient to develop immediate type hypersensitivity and that a single intra-airway challenge is capable of triggering pulmonary responses. To investigate potential cross-reactivity, mice were sensitized to AHCP and, challenged by a single IA with a second platinum compound, ATCP. Compared to non-sensitized mice challenged with ATCP, these mice exhibited an IR, responsiveness to Mch, and eosinophilic infiltration in the lungs similar to that achieved with AHCP challenge, thus demonstrating cross-reactivity.

Assessment of the Cytotoxic and Immunomodulatory Effects of Substances in Human Precision-cut Lung Slices.

Respiratory diseases in their broad diversity need appropriate model systems to understand the underlying mechanisms and enable development of new therapeutics. Additionally, registration of new substances requires appropriate risk assessment with adequate testing systems to avoid the risk of individuals being harmed, for example, in the working environment. Such risk assessments are usually conducted in animal studies. In view of the 3Rs principle and public skepticism against animal experiments, human alternative methods, such as precision-cut lung slices (PCLS), have been evolving. The present paper describes the ex vivo technique of human PCLS to study the immunomodulatory potential of low-molecular-weight substances, such as ammonium hexachloroplatinate (HClPt). Measured endpoints include viability and local respiratory inflammation, marked by altered secretion of cytokines and chemokines. Pro-inflammatory cytokines, tumor necrosis factor alpha (TNF-α), and interleukin 1 alpha (IL-1α) were significantly increased in human PCLS after exposure to a sub-toxic concentration of HClPt. Even though the technique of PCLS has been substantially optimized over the past decades, its applicability for the testing of immunomodulation is still in development. Therefore, the results presented here are preliminary, even though they show the potential of human PCLS as a valuable tool in respiratory research.

Assessment of the Cytotoxic and Immunomodulatory Effects of Substances in Human Precision-cut Lung Slices

Respiratory diseases in their broad diversity need appropriate model systems to understand the underlying mechanisms and enable development of new therapeutics. Additionally, registration of new substances requires appropriate risk assessment with adequate testing systems to avoid the risk of individuals being harmed, for example, in the working environment. Such risk assessments are usually conducted in animal studies. In view of the 3Rs principle and public skepticism against animal experiments, human alternative methods, such as precision-cut lung slices (PCLS), have been evolving. The present paper describes the ex vivo technique of human PCLS to study the immunomodulatory potential of low-molecular-weight substances, such as ammonium hexachloroplatinate (HClPt). Measured endpoints include viability and local respiratory inflammation, marked by altered secretion of cytokines and chemokines. Pro-inflammatory cytokines, tumor necrosis factor alpha (TNF-α), and interleukin 1 alpha (IL-1α) were significantly increased in human PCLS after exposure to a sub-toxic concentration of HClPt. Even though the technique of PCLS has been substantially optimized over the past decades, its applicability for the testing of immunomodulation is still in development. Therefore, the results presented here are preliminary, even though they show the potential of human PCLS as a valuable tool in respiratory research.

Activation of T cells by dendritic cells exposed to a reference sensitizer: Towards a promising model to assess the allergenic potential of chemicals.

Low molecular weight chemicals constitute one of the major causes of occupational allergies. European legislation on chemicals recommends limiting the use of in vivo models for assessing the sensitizing potential of chemicals, and encourages the development of integrated alternative methods. An in vitro mouse model of bone marrow-derived dendritic cells (BMDCs) that showed good accuracy (75%) and sensitivity (69%) has previously been developed to assess the sensitizing potential of chemicals. To assess the ability of BMDCs to activate T cells (TCs) in vitro. BMDCs pre-exposed to the reference sensitizer ammonium hexachloroplatinate (AHCP) were co-cultured with different subpopulations of TCs. TC activation was assessed by surface marker expression, proliferation, and cytokine release. The results showed significant activation of TCs co-cultured with dendritic cells pre-exposed to AHCP as evaluated by CD124 expression, proliferation, and cytokine secretion. Moreover, the response of TCs appeared to be Th2-oriented. Naive TCs were shown to be involved in this response, and the removal of regulatory TCs did not improve the cell response. The BMDCs used in this previously developed model appear to have the ability to activate TCs, confirming that the BMDC model represents a reliable assay for assessing the sensitizing potential of chemicals.

FePt electrodeposited from ionic liquids on Si(111) substrate

This work concerns FePt nanowires electrodeposited from electrolyte of E1 [ammonium hexachloroplatinate (25 mM L− 1), 1-ethyl-3-methylimidazolium chloride (25 mM L− 1)], iron dichloride (315 mM L− 1) and glycol (50 mL) at 393 K. FePt nanowires and films were electrodeposited by controlling the electrodeposited time under suitable potential in E1. FePt nanowires were prepared at different times of 600, 800 and 1000 s when deposition potential was − 2·0 V versus Ag/AgCl. The SEM patterns proved that FePt nanowires were prepared at suitable deposition time (600–1000 s). The X-ray diffraction pattern indicated that the face centre tetragonal structure of FePt nanowires was obtained. Magnetic hysteresis loops showed that aggregation could decrease the coercivity, and some nanowires were larger than the mean diameter, which exhibited a comparatively large ferromagnetic behaviour.

Process development and optimization for platinum recovery from PEM fuel cell catalyst

This paper presents the development of an efficient hydrometallurgical recovery process of platinum from Pt catalyst of PEMFC electrodes at laboratory scale, whereby leaching, Pt separation, precipitation and filtration steps were combined in order to optimize the recovery process. The efficiencies of two different leaching agents (H2O2/HCl and HNO3/HCl) and two different separation methods (liquid–liquid extraction and ion exchange resins) were compared in this study. Finally the platinum was recovered by precipitation as ammonium hexachloroplatinate (NH4)2PtCl6 (a PEMFC catalyst precursor) at the outlet of each process alternative. Thus four different process alternatives were tested and compared.At first the experiments were performed with Pt/C particles and hexachloroplatinic acid in order to study the influence of several experimental parameters on platinum recovery efficiency. Then the real PEMFC catalyst coated membranes (CCMs) were treated according to the optimized leaching/recovery process. Finally, the most efficient process alternative gave a 76% Pt recovery yield from CCMs.

Lung function changes in mice sensitized to ammonium hexachloroplatinate

Occupational exposure to halogenated platinum salts can trigger the development of asthma. The risk to the general population that may result from the use of platinum in catalytic converters and its emerging use as a diesel fuel additive is unclear. To investigate pulmonary responses to platinum, we developed a mouse model of platinum hypersensitivity. Mice were sensitized through application of ammonium hexachloroplatinate (AHCP) to the shaved back on days 0, 5 and 19, and to each ear on days 10, 11 and 12. On days 24 and 29, mice were challenged by oropharyngeal aspiration with AHCP in saline. Before and immediately after challenge, pulmonary responses were assessed using whole body plethysmography (WBP). A dose-dependent increase in immediate responses was observed in AHCP-sensitized and challenged mice. On days 26 and 31, changes in ventilatory responses to methacholine (Mch) aerosol were assessed by WBP; dose-dependent increases in Mch responsiveness occurred in sensitized mice. Lymph node cell counts indicate a proliferative response in lymph nodes draining the sites of application. Bronchoalveolar lavage fluid harvested from sensitized mice contained an average of 5% eosinophils compared to less than 0.5% in non-sensitized mice (p < 0.05); significant increases in total serum immunoglobulin E were observed for all sensitized mice. Although a second airway challenge on day 29 affected some results, only one airway challenge was needed to observe changes in lung function.

Development and utilization of an ex vivo bromodeoxyuridine local lymph node assay protocol for assessing potential chemical sensitizers

The murine local lymph node assay (LLNA) is widely used to identify chemicals that may cause allergic contact dermatitis. Exposure to a dermal sensitizer results in proliferation of local lymph node T cells, which has traditionally been measured by in vivo incorporation of [(3) H]methyl thymidine. A more recent non-isotopic variation of the assay utilizes bromodeoxyuridine (BrdU) incorporation in vivo. To further improve the utility of this assay, we developed an ex vivo BrdU labeling procedure eliminating the need for in vivo injections. The results of this assay correctly identified a strong sensitizer (i.e., trimellitic anhydride) as well as weak/moderate sensitizers (i.e., eugenol, cinnamaldehyde and hexylcinnaminic aldehyde). As anticipated, neither non-sensitizers isopropanol and lactic acid nor the false negative chemical nickel II sulfate hexahydrate induced a positive threshold response in the assay. The results of this assay are in close agreement with those of the in vivo LLNA:BrdU-enzyme-linked immunosorbent assay labeling procedure. We also used the ex vivo BrdU LLNA procedure to evaluate ammonium hexachloroplatinate, ammonium tetrachloroplatinate and cis-diamminedichloroplatinum(II) and the assay correctly identified them as sensitizers based on the calculation of EC2 values. We conclude that this ex vivo BrdU labeling method offers predictive capacity comparable to previously established LLNA protocols while eliminating animal injections and the use of radioisotope. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Assessment of immunotoxicity induced by chemicals in human precision-cut lung slices (PCLS)

Occupational asthma can be induced by a number of chemicals at the workplace. Risk assessment of potential sensitizers is mostly performed in animal experiments. With increasing public demand for alternative methods, human precision-cut lung slices (PCLS) have been developed as an ex vivo model.Human PCLS were exposed to increasing concentrations of 20 industrial chemicals including 4 respiratory allergens, 11 contact allergens, and 5 non-sensitizing irritants. Local respiratory irritation was characterized and expressed as 75% (EC25) and 50% (EC50) cell viability with respect to controls. Dose–response curves of all chemicals except for phenol were generated. Local respiratory inflammation was quantified by measuring the production of cytokines and chemokines. TNF-α and IL-1α were increased significantly in human PCLS after exposure to the respiratory sensitizers trimellitic anhydride (TMA) and ammonium hexachloroplatinate (HClPt) at subtoxic concentrations, while contact sensitizers and non-sensitizing irritants failed to induce the release of these cytokines to the same extent. Interestingly, significant increases in TH1/TH2 cytokines could be detected only after exposure to HClPt at a subtoxic concentration.In conclusion, allergen-induced cytokines were observed but not considered as biomarkers for the differentiation between respiratory and contact sensitizers. Our preliminary results show an ex vivo model which might be used for prediction of chemical-induced toxicity, but is due to its complex three-dimensional structure not applicable for a simple screening of functional and behavior changes of certain cell populations such as dendritic cells and T-cells in response to allergens.

FePt magnetic multilayers electrodeposited from non-aqueous liquids

FePt magnetic multilayers were pulse electrodeposited from the mixture of ammonium hexachloroplatinate and iron dichloride in ionic liquids based on glycol (EG) and 1-ethyl-3-methylimidazolium chloride (EMIC). The chelate effect and electrochemical behaviour of the EMIC with the ions were determined by ultraviolet–visible spectra and cyclic voltammetry respectively. The iron atomic content in the FePt films ranged from 0·4 to 81·0 at-% when deposition potentials changed from 1·0 to −2·0 V(Ag/AgCl) in electrodeposition system with the EG (50 mL), ammonium hexachloroplatinate (25 mM L−1), iron dichloride (175 mM L−1) and EMIC (25 mM L−1) at 393 K. Fe50Pt50 thin films with smooth surface (50 at-% iron layer in FePt film) and the multilayer cross-section were obtained. Fct structural FePt multilayer was obtained based on X-ray diffraction pattern. Magnetic hysteresis loops showed that the multilayer possessed a magnetic anisotropic behaviour.

NCTC 2544 and IL-18 production: A tool for the identification of contact allergens

Progress in understanding the mechanisms of skin sensitization, provides us with the opportunity to develop in vitro tests as an alternative to in vivo sensitization testing.Keratinocytes play a key role in all phases of skin sensitization. We have recently identified interleukin-18 (IL-18) production in keratinocyte as a potentially useful endpoint for determination of contact sensitization potential of low molecular weight chemicals. The aim of the present article is to further exploit the performance of the NCTC 2544 assay.NCTC 2544 is a commercially available skin epithelial-like cell line originating from normal human skin, which posses a good expression of cytochrome P450-dependent enzymatic activities. Cells were exposed to contact allergens (2-bromo-2-bromomethyl glutaronitrile, cinnamaldehyde, citral, diethylmaleate, dinitrochlorobenzene, glyoxal, 2-mercaptobenzothiazole, nickel sulfate, 4-nitrobenzylbromide, oxazolone, penicillin G, resorcinol, tetramethylthiuram disulfide), to pre- pro-haptens (cinnamyl alcohol, eugenol, isoeugenol, p-phenylediamine), to respiratory allergens (ammonium hexachloroplatinate, diphenylmethane diisocyanate, glutaraldehyde, hexamethylenediisocyanate, maleic anhydride, trimellitic anhydride) and to irritants (benzaldehyde, cholorobenzene, diethylphtalate, hydrobenzoic acid, lactic acid, octanoic acid, phenol, salicylic acid, sodium lauryl sulphate, sulfamic acid). Cell associated IL-18 was evaluated 24 later by ELISA. At not-cytotoxic concentrations (cell viability higher of 80%, as assessed by MTT reduction assay), all contact sensitizers, including pre-pro-haptens, induced a dose-related increase in IL-18, whereas both irritants, with the exception of sulfamic acid, and respiratory allergens failed. A total of 33 chemicals were tested, with an overall accuracy of 97%.Overall, results obtained indicated that cell-associated IL-18 might provide an in vitro tool for identification and discrimination of contact vs. respiratory allergens and/or irritants.

Ammonium hexachloroplatinate (AHCP) exposure results in a T helper (Th) 2 profile

Ammonium hexachloroplatinate (AHCP) exposure results in a T helper (Th) 2 profile

Alcohol reduction-mediated preparation of a nano-scale Pt/C electrocatalyst for the oxygen reduction reaction in PEM fuel cells

A nano-scale Pt/C electrocatalyst for oxygen reduction in PEM fuel cells was prepared by alcohol-mediated reduction of the PtCl 6 2− ion complex on the carbon Vulcan XC-72. The effects of various parameters, including the types of precursor and reducing agent and their concentrations, the initial solution pH and the reaction time, were explored. The preliminary results indicated that the electrocatalyst prepared using ammonium hexachloroplatinate ((NH 4) 2PtCl 6) as the Pt 2+ source provided a similar catalytic efficiency as that prepared from hexachloroplatinic acid (H 2PtCl 6). The nano-scale Pt/C electrocatalyst prepared using methanol (CH 3OH) as a reducing agent provided the smallest sized platinum particles with a uniform distribution in the nanometer range, a good particle dispersion and a high Pt content compared with that prepared using ethanol (C 2H 5OH) or 2-propanol (C 3H 7OH). The electrocatalyst prepared in an acidic solution yielded smaller sized platinum particles and a higher Pt content than that prepared in a basic solution. In addition, the concentration of the reducing agent and reaction time slightly affected both the Pt particle size and the Pt yield of the obtained electrocatalyst. Under apparent optimal conditions, the nano-scale Pt/C electrocatalyst had an electrochemical surface area of ∼39.7 m 2/g, which was ∼1.9-fold higher than that of the commercial one. The performance of the electrocatalyst was also tested in a single PEM fuel cell in a H 2/O 2 atmosphere where compared to a commercial electrode a lower activation loss but higher ohmic loss was observed.