Silica-supported chitosan–platinum complex catalyst for hydrosilylation reactions

Silica-supported chitosan–platinum complex was prepared and characterized by ICP-AES, FT-IR, and XPS, respectively. The complex as catalyst was found to display high catalytic activity in the hydrosilylation reaction of allyl glycidyl ether with triethoxysilane for the first time. It can be recovered by simple filtration and reused for six times without significant loss of activity.     

Cyanostilbene-based near-infrared emissive platinum(Ⅱ) metallacycles for cancer theranostics

In this work,a near-infrared emissive dipyridyl ligand was synthesized and used to prepare three platinum(Ⅱ) metallacycles with different shapes via metal-coordination-driven self-assembly with different platinum(Ⅱ) precursors.These metallacycles were further used for both cell imaging and cancer therapy,offering a new type of theranostic agents towards cancer treatment.     

A shotgun approach for the identification of platinum–protein complexes

A shotgun approach including peptide-based OFFGEL-isoelectric focusing (IEF) fractionation has been developed with the aim of improving the identification of platinum-binding proteins in biological samples. The method is based on a filter-aided sample preparation (FASP) tryptic digestion under denaturing and reducing conditions of cisplatin–, oxaliplatin–, and carboplatin–protein complexes, followed by OFFGEL-IEF separation of the peptides. Any risk of platinum loss is minimized throughout the procedure due to the removal of the reagents used after each stage of the FASP method and the absence of thiol-based reagents in the focusing buffer employed in the IEF separation. The platinum–peptide complexes stability after the FASP digestion and the IEF separation was confirmed by size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS). The suitability of peptide-based OFFGEL-IEF fractionation for reducing the sample complexity for further nano-liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS/MS) analysis has been demonstrated, allowing the detection of platinum-containing peptides, with significantly lower abundance and ionization efficiency than unmodified peptides. nLC-MS/MS analysis of selected OFFGEL-IEF fractions from tryptic digests with different complexity degrees: standard human serum albumin (HSA), a mixture of five proteins (albumin, transferrin, carbonic anhydrase, myoglobin, and cytochrome-c) and human blood serum allowed the identification of several platinum–peptides from cisplatin–HSA. Cisplatin-binding sites in HSA were elucidated from the MS/MS spectra and assessed considering the protein three-dimensional structure. Most of the potential superficial binding sites available on HSA were identified for all the samples, including a biologically relevant cisplatin-cross-link of two protein domains, demonstrating the capabilities of the methodology.

Open image in new window

Graphical Abstract Graphical abstract shows the several steps involved in the identification of platinum-protein complexes: FASP digestion of proteins, peptide fractionation by OFFGEL-IEF and identification of Pt-complexes by nLC-ESIMS/MS

     

Thin target excitation functions for (α , xn) reactions on osmium targets for platinum radiotracer production

Thin- and thick-target excitation functions of ^188,189,191Ptradionuclides were experimentally determined by cyclotron irradiation, usingnuclear reactions nat ^Os( ,xn) in the energy range up to38 MeV with the Scanditronix-MC40 cyclotron of the Joint Research Centre-Ispra(Italy) of the European Union. Radionuclidic, radiochemical and chemical puritieshave been also measured by use of analytical and radioanalytical techniques.In this paper the result of the experimental thin target excitation functionsof ^188,189,191Pt radiotracers produced via nat ^Os(,xn) reactions are presented. Two stacks of thin osmium targets were irradiatedat 38 and 28 MeV, respectively. Analytical fittings of the excitation functionsare also presented.     

Multi-dimensional Pt–Mo/Co@NC nanocomposites with low platinum contents for methanol oxidation

Journal of Solid State Electrochemistry - The high cost, CO poisoning, and slow electro-oxidation kinetics of Pt-based noble metal catalysts limit the merchandizing of direct methanol fuel cell....     

A facile chemical reduction method for synthesis of platinum–iron catalysts on carbon fiber papers for methanol oxidation

To enhance catalytic activity and durability for methanol oxidation reaction (MOR), we have fabricated bimetallic Pt–Fe catalysts on carbon fiber papers (denoted as Pt–Fe@CFP) by a facile chemical reduction method using iron as the precursor, ascorbic acid and sodium hypophosphite as the reductants, respectively. When ascorbic acid is using as the reductant, the Pt–Fe@CFP catalysts are composed of platinum and disordered Pt–Fe phases. The atomic ratio between Pt and Fe can be adjusted by altering deposition conditions. The Pt–Fe@CFP catalysts with Pt/Fe ratio of 1.1, which deposited with surfactant CTAB in bath at room temperature, exhibit excellent catalytic activity and stability in MOR. However, when sodium hypophosphite is employed as the reductant, the co-deposition of phosphorus would lead to a decreased catalytic performance in MOR.     

Gold–platinum alloy nanowires as highly sensitive materials for electrochemical detection of hydrogen peroxide

The exploitation of the unique electrical properties of nanowires requires an effective assembly of nanowires as functional materials on a signal transduction platform. This paper describes a new strategy to assemble gold–platinum alloy nanowires on microelectrode devices and demonstrates the sensing characteristics to hydrogen peroxide. The alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current. The composition, morphology and alloying structures of the nanowires were characterized, revealing a single-phase alloy characteristic, highly monodispersed morphology, and controllable bimetallic compositions. The alloy nanowires were shown to exhibit electrocatalytic response characteristics for the detection of hydrogen peroxide, exhibiting a high sensitivity, low detection limit, and fast response time. The nanowire's response mechanism to hydrogen peroxide is also discussed in terms of the synergistic activity of the bimetallic binding sites, which has important implications for a better design of functional nanowires as sensing materials for a wide range of applications.     

Electrochemical deposition of platinum nanoparticles in multiwalled carbon nanotube–Nafion composite for methanol electrooxidation

Platinum nanoparticles were successfully deposited within a multiwalled carbon nanotube (MWCNT)–Nafion matrix by a cyclic voltammetry method. A Pt(IV) complex was reduced to platinum nanoparticles on the surface of MWCNTs. The resulting Pt nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Pt–MWCNT–Nafion nanocomposite film-modified glassy carbon electrode had a sharp hydrogen desorption peak at about −0.2 V vs. Ag/AgCl (3 M) in a solution of 0.5 M H₂SO₄, which is directly related to the electrochemical activity of the Pt nanoparticles presented on the surface of MWCNTs. The electrocatalytic properties of the Pt–MWCNT–Nafion nanocomposite-modified glassy carbon electrode for methanol electrooxidation were investigated by cyclic voltammetry in a 2 M CH₃OH + 1 M H₂SO₄ solution. In comparison with the Pt-coated glassy carbon electrode and the Pt–Nafion modified glassy carbon electrode, the Pt–MWCNT–Nafion-modified electrode had excellent electrocatalytic activity toward methanol electrooxidation. The stability of the Pt–MWCNT–Nafion nanocomposite-modified electrode had also been evaluated.     

Novel separation method for highly sensitive speciation of cancerostatic platinum compounds by HPLC–ICP–MS

A high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICP–MS) method is presented for analysis of cisplatin, monoaquacisplatin, diaquacisplatin, carboplatin, and oxaliplatin in biological and environmental samples. Chromatographic separation was achieved on pentafluorophenylpropyl-functionalized silica gel. For cisplatin, carboplatin, and oxaliplatin limits of detection of 0.09, 0.10, and 0.15 g L^–1, respectively, were calculated at m/z 194, using aqueous standard solutions. (3 L injection volume). The method was utilized for model experiments studying the stability of carboplatin and oxaliplatin at different chloride concentrations simulating wastewater and surface water conditions. It was found that a high fraction of carboplatin is stable in ultrapure water and in solutions containing 1.5 mol L^–1 Cl^–, whereas oxaliplatin degradation was increased by increasing the chloride concentration. In order to support the assessment of oxaliplatin eco-toxicology, the method was tested for speciation of patient urine. The urine sample contained more than 17 different reaction products, which demonstrates the extensive biotransformation of the compound. In a second step of the study the method was successfully evaluated for monitoring cancerostatic platinum compounds in hospital waste water.     

Synthesis of PEGylated hyaluronic acid for loading dichloro(1,2-diaminocyclohexane)platinum(Ⅱ)(DACHPt) in nanoparticles for cancer treatment

Dichloro(1,2-diaminocyclohexane)platinum(II)(DACHPt), a cisplatin(CDDP) analog, has shown lower toxicity than CDDP and no cross-resistance with CDDP in many CDDP-resistant cancers. PEGylated hyaluronan(m PEG-HA) is an m PEG conjugated with hyaluronan biodegradable polymer which is a naturally occurring biopolymer in the interstitium, is primarily cleared by the lymphatic system. m PEGhyaluronan–DACHPt(PEG-HA–Pt) conjugate could circulate long-term in the bloodstream and increase DACHPt concentration in the tumor site and decrease systemic toxicity. m PEG-HA conjugates with the range of 1%–5% substitution were synthesized, and the structures were confirmed by1 H NMR and IR. The particle size of DACHPt incorporated with m PEG-HA was about 86 nm and the loading content and efficiency were about 19%(w/w) and 86%, respectively. The synthesized m PEG-HA with different PEG substitution degrees presented non toxicity, and the cell viability of DACHPt loaded in m PEG-HA nanoparticles increased with increasing doses of DACHPt. DACHPt release from nanoparticles slightly decreased with increasing PEG substitution degree from 1% to 5% at 37 8C, pH 7.4 PBS solution. The DACHPt loaded in m PEG-HA nanoparticles significantly inhibited the growth of A549 xenografts in nude mice when compared to the DACHPt loaded in HA nanoparticles and the control group after 4 weeks treatment(p 0.01 compared with control). The body weight change curve shows that the mice weight loss was less than 5% by treating with both DACHPt loaded in m PEG-HA and HA nanoparticles. In conclusion, a novel DACHPt loaded m PEG-HA delivery system was developed with sustained release and increased platinum concentration in the tumor.     

Ion beam induced deposition of platinum carbon composite electrodes for combined atomic force microscopy–scanning electrochemical microscopy

In the present study, ion beam induced deposition (IBID) of platinum carbon (PtC) composite electrodes is evaluated for combined atomic force microscopy–scanning electrochemical microscopy (AFM–SECM) probes. After deposition, the PtC composite materials are post-treated using focused ion beam (FIB) milling to decrease the carbon content of the material. It is shown that this treatment leads to an improvement of electrode characteristics for selected analytes, including the oxidation of potassium hexacyanoferrate(II) trihydrate (Fe(CN)₆^4?) and hydrogen peroxide (H₂O₂). Moreover, the proposed approach is compatible with microfabricated AFM–SECM probes for increasing the AFM tip-integrated electroactive area while maintaining the geometric dimensions, which is important for imaging biosensor development.     

Vapor- and mechanical-grinding-triggered color and luminescence switches for bis(σ-fluorophenylacetylide) platinum(II) complexes

Square-planar bis(σ-fluorophenylacetylide) platinum(II) complexes [Pt(Me(3)SiC≡CbpyC≡C-SiMe(3))(C≡CC(6)H(4)F)(2)] (C≡CC(6)H(4)F-2 for 2, C≡CC(6)H(4)F-3 for 3, and C≡CC(6)H(4)F-4 for 4; Me(3)SiC≡CbpyC≡CSiMe(3)=5,5'-bis(trimethylsilylethynyl)-2,2'-bipyridine) were prepared and were characterized by spectroscopic and luminescence studies, and X-ray crystallography. The color and luminescence of crystalline complex 3 is specifically sensitive to CHCl(3) vapor to afford 140-180 nm of luminescence vapochromic redshift, which is useful for specific detection of CHCl(3) vapor. Complex 4 displays selective luminescence vapochromic properties to CH(2)Cl(2) and CHCl(3) vapors with a luminescence vapochromic shift response of ca. 150-200 nm. Interestingly, complexes 2-4 exhibit reversible, and naked-eye perceivable, mechanical stimuli-responsive color and luminescence changes. When solid species 2-4 are crushed gently or ground, the crystalline state is converted to an amorphous phase. Meanwhile, bright yellow-orange luminescence in the crystalline species is converted to dark red under UV light irradiation with 100-160 nm of mechanochromic shift response. A vapochromic or mechanochromic cycle was monitored by dynamic variations in emission spectra and X-ray diffraction (XRD) patterns. The halohydrocarbon vapor- or mechanical-grinding-triggered color and luminescence switches are most likely correlated to a shorted intermolecular Pt-Pt distance as that revealed in vapochromic species 4·0.5 CH(2)Cl(2) by X-ray crystallography, thus leading to an increased contribution from intermolecular Pt-Pt interaction as demonstrated by DTF computational studies.     

Structure and properties of Pd–Mn hexaaluminate catalysts modified with platinum for the high-temperature oxidation of methane

The effect of Pt additives on the catalytic characteristics of a Pd-containing catalyst based on manganese hexaaluminate was studied. It was found that the bimetallic PtPd-containing catalysts based on MnLaAl₁₁O₁₉ with the Pt/Pd atomic ratio smaller than 0.25 exhibited a comparable or somewhat smaller activity in the methane oxidation, but their stability at elevated temperatures and gas flow rates was higher than that of the Pd-based catalyst. The state of the active constituent of the resulting catalysts was investigated. Main correlations between the state of the active component and the catalytic activity were revealed.     

Microwave spectroscopy of platinum monofluoride and platinum monochloride in the X 2Π(3/2) states

Platinum monofluoride (PtF) and platinum monochloride (PtCl) were detected in the gas phase using a source-modulated microwave spectrometer. The PtF and PtCl radicals were generated in a free space cell using the sputtering reaction from a platinum sheet placed on the inner surface of a stainless steel cathode through a dc glow discharge plasma of CF(4) and Cl(2), respectively, diluted with Ar. Rotational transitions were measured in the region between 150 and 313 GHz. Rotational, centrifugal distortion, and several fine- and hyperfine-structure constants were determined by a least-squares analysis. The observed fine-structure spectral patterns indicate that both PtF and PtCl radicals have the (2)Π(3/2) electronic ground states, while the related cyanide PtCN and hydride PtH radicals have the (2)Δ(5/2) electronic ground states.     

Exo-H- andendo-H-η4-pentamethylcyclopentadiene complexes of platinum

A mixture ofendo-H andexo-H isomers (1a and1b) of the (⁴-C₅Me₅H)PtCl₂ complex was prepared by the reaction of K₂PtCl₄ with C₅Me₅H in MeOH. The mixture of isomers reacts with CpTl in the presence of TiBF₄ to give a novel complex, [(⁴-C₅Me₅H)Pt(⁵-C₅H₅)]⁺BF₄ ^–, as a mixture ofendo-H- andexo-H-isomers (2a and2b). The data of¹H and¹³C NMR spectroscopy of the resulting complexes are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 514–517, March, 1994.     

Polymer-anchored platinum complexes as catalysts for the Baeyer–Villiger oxidation of ketones: preparation and catalytic properties

The preparation of a variety of catalysts obtained by ion exchange of the complex [(dppb)Pt(μ−OH)]₂²⁺ with sulfonated styrene–divinylbenzene copolymers is reported. Copolymers used are commercial ion exchange resins containing either 4% or 20% DVB and they were loaded with either Li⁺ or NBu₄⁺ prior to exchange with the Pt complex. Metal loading in the heterogenized catalysts is in the range 2–8% by weight. Their catalytic properties in the Baeyer–Villiger oxidation of methylcyclohexanone with hydrogen peroxide appear to be best in terms of activity and productivity either in neat ketone or in EtOH as the solvent. The use of commercial resins with high exchange capacity prevents the use of DCE as the solvent, i.e., the optimum conditions for the homogeneous system, thereby leading to activities and productivities that are generally lower than their homogeneous counterpart. A discussion on the influence of the philicity properties of the support with respect to the performance of the catalyst is reported.     

Catalytic systems based on platinum and heteropoly compounds for oxidation of hydrocarbons with a dioxygen—dihydrogen gaseous mixture

The oxidation of cyclohexane, saturated and aromatic hydrocarbons with an O₂—H₂ gaseous mixture was applied to study the catalytic properties of bicomponent systems based on platinum and heteropoly compounds (HPC). The consumption of gases and the yield of the products depend on the surface area, accessibility of the platinum species to the reactant, and composition of the HPC. The solid Pt samples suspended in an HPC solution, the Pt(5%)—PMo₁₂/Al₂O₃ bicomponent supported system, and the solid bicomponent sample prepared from the [Pt(NH₃)₄][H₂PMo₁₂O₄₀]₂·7H₂O complex salt were used as catalysts. Among the catalysts with the same molar compositions of the active components, the bicomponent materials are much more active in the oxidation than a combination of the Pt catalyst with an HPC solution. The bulk catalyst is a crystalline solid substance with the HPC structure with incorporated Pt species. Molybdenum is predominantly oxidized, and platinum is present in both the reduced and ionic states. The oxidation of saturated hydrocarbons affords alcohols and ketones. The yield of the positional isomers of the oxygenated products increases in the series primary << secondary < tertiary C-atoms. Benzene and toluene are converted into the corresponding phenols in equal yields. The scheme proposed for oxidation assumes the participation of the active hydroxyl radical.     

Determination of trace platinum by supramolecular catalytic kinetic spectrofluorimetry of β–cyclodextrin–platinum–KBrO3–salicylaldehyde furfuralhydrazone

A supramolecular catalytic kinetic spectrofluorimetric method was developed for the determination of platinum(IV) and the possible mechanism of catalytic reaction was discussed. The method was based on the fluorescence-enhancing reaction of salicylaldehyde furfuralhydrazone (SAFH) with potassium bromate, which was catalysed by platinum(IV) in a water–ethanol medium. β–Cyclodextrin (β-CD) obviously sensitized the determination at pH 5.20 and 25°C. Under optimum conditions, the β-CD–platinum–KBrO₃–SAFH supramolecular kinetic catalytic reaction system had excitation and emission maxima at 372 and 461 nm, respectively. The linear range of this method was 0.60–180 ng ml⁻¹ with a relative standard deviation of 1.2%, and the detection limit was 0.18 ng ml⁻¹. Investigation of the mechanism and the effects of interferences is presented. The proposed method was applied successfully to determine trace platinum(IV) in the chemotherapeutic drug cisplatin and serum from patients with satisfactory results.      

Heterometallic binuclear complexes involving the mercury—platinum bond as a source of a platinum carbenoid in reactions with fullerene-60

The cleavage of two σ-bonds and the formation of a metallocomplex, (η²-C₆₀)Pt(PPh₃)₂, occur in a new reaction between fullerene-60 and binuclear heterometallic compounds having a mercury-platinum bond (retro-insertion promoted by C₆₀). One of these,trans- Ph₂CHCH₂HgPt(PPh₃)₂Br,1, which contains an electron-donating group at the mercury atom, reacts two orders of magnitude faster thancis-(CF₃)₂CFHgPt(PPh₃)₂CH=CPh₂,2, which has an electron-withdrawing substituent at mercury. An asymmetrical organomercury compound is the second product of the reaction. The reactants and products have been characterized by spectroscopic data (¹H,³¹P NMR, UV-VIS) and elemental analyses. Compound 2, which is more stable to retro-insertion, gives a Pt-centered free radical upon photolysis. This was used for the free-radical functionalization of C₆₀. The platinumfullerenyl radicalcis-C₆₀Pt(PPh₃)₂R² was identified by EPR spectroscopy.