Selective methane chlorination to methyl chloride by zeolite Y-based catalysts

The CH₄ chlorination over Y zeolites was investigated to produce CH₃Cl in a high yield. Three different catalytic systems based on Y zeolite were tested for enhancement of CH₄ conversion and CH₃Cl selectivity: (i) HY zeolites in H⁺-form having various Si/Al ratios, (ii) Pt/HY zeolites supporting Pt metal nanoparticles, (iii) Pt/NaY zeolites in Na⁺-form supporting Pt metal nanoparticles. The reaction was carried out using the gas mixture of CH₄ and Cl₂ with the respective flow rates of 15 and 10 mL min⁻¹ at 300–350 °C using a fixed-bed reactor under a continuous gas flow condition (gas hourly space velocity = 3000 mL g⁻¹ h⁻¹). Above the reaction temperature of 300 °C, the CH₄ chlorination is spontaneous even in the absence of catalyst, achieving 23.6% of CH₄ conversion with 73.4% of CH₃Cl selectivity. Under sufficient supplement of thermal energy, Cl₂ molecules can be dissociated to two chlorine radicals, which triggered the C-H bond activation of CH₄ molecule and thereby various chlorinated methane products (i.e., CH₃Cl, CH₂Cl₂, CHCl₃, CCl₄) could be produced. When the catalysts were used under the same reaction condition, enhancement in the CH₄ conversion was observed. The Pt-free HY zeolite series with varied Si/Al ratios gave around 27% of CH₄ conversion, but there was a slight decrease in CH₃Cl selectivity with about 64%. Despite the difference in acidity of HY zeolites having different Si/Al ratios, no prominent effect of the Si/Al ratios on the catalytic performance was observed. This suggests that the catalytic contribution of HY zeolites under the present reaction condition is not strong enough to overcome the spontaneous CH₄ chlorination. When the Pt/HY zeolite catalysts were used, the CH₄ conversion reached further up to 30% but the CH₃Cl selectivity decreased to 60%. Such an enhancement of CH₄ conversion could be attributed to the strong catalytic activity of HY and Pt/HY zeolite catalysts. However, both catalysts induced the radical cleavage of Cl₂ more favorably, which ultimately decreased the CH₃Cl selectivity. Such trade-off relationship between CH₄ conversion and CH₃Cl selectivity can be slightly broken by using Pt/NaY zeolite catalyst that is known to possess Frustrated Lewis Pairs (FLP) that are very useful for ionic cleavage of H₂ to H⁺ and H⁻. Similarly, in the present work, Pt/NaY(FLP) catalysts enhanced the CH₄ conversion while keeping the CH₃Cl selectivity as compared to the Pt/HY zeolite catalysts.     

Spectrofluorimetric determination of iridium(IV) traces using 4-pyridone derivatives

A new spectrofluorimetric determination of iridium(IV) with 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX) or 3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone (HY) is reported. Iridium(IV) react with HX or HY and chelates were extracted into chloroform or dichloromethane. The organic phase showed fluorescence. The fluorescence measurements to quantify iridium were carried out in its fluorescent band centred at λ_ex=373 nm and λ_em=480 nm. Under optimal conditions, the calibration graphs were linear over the concentration range of 0.1-7.6 μg ml⁻¹ of iridium for Ir(IV)-HX and 0.1-5.8 μg ml⁻¹ for Ir(IV)-HY with a correlation coefficients of 0.999 and 0.992 and relative standard deviation of ±1.1%.The method is free from interference by Rh(III) and Pt(IV), which normally interfere with other methods. Iridium can be determined in the presence of 300-fold excess of rhodium(III) and 10-fold excess of platinum(IV).The method was applied successfully to the determination of iridium in some synthetic mixtures and mineral sample gave satisfactory results.     

Quasi-equilibrated temperature programmed desorption and adsorption: A new method for determination of the isosteric adsorption heat

Temperature programmed desorption and adsorption (TPDA) studied under quasi-equilibrium conditions using typical flow TPD setup equipped with a chromatographic TCD detector has been found a good method of obtaining the equilibrium data characterizing adsorption of n-hexane on high silica HZSM-5 and HY zeolites. The equilibrium control of sorption has been confirmed by linearity of the isosters constructed from the TPDA profiles. For HZSM-5 it was corroborated by very good agreement obtained in fitting the experimental data with the model based on the dual site Langmuir (DSL) adsorption function. The values of the adsorption enthalpy and entropy, either determined from the adsorption isosters or as the fitted model parameters, were close to the literature data. Increase of the isosteric adsorption heat of hexane with coverage was observed for both zeolites (72-90 kJ mol⁻¹ for HZSM-5 and 46-61 kJ mol⁻¹ for HY).     

Synthesis of Na-A and/or Na-X zeolite/porous carbon composites from carbonized rice husk

Na-A and/or Na-X zeolite/porous carbon composites were prepared under hydrothermal conditions by NaOH dissolution of silica first from carbonized rice husk followed by addition of NaAlO₂ and in situ crystallization of zeolites i.e., using a two-step process. When a one-step process was used, both Na-A and Na-X zeolites crystallized on the surface of carbon. Na-A or Na-X zeolite crystals were prepared on the porous carbonized rice husk at 90 °C for 2-6 h by changing the SiO₂/Al₂O₃, H₂O/Na₂O and Na₂O/SiO₂ molar ratios of precursors in the two-step process. The surface area and NH₄⁺-cation exchange capacity (CEC) of Na-A zeolite/porous carbon were found to be 171 m²/g and 506 meq/100 g, respectively, while those of Na-X zeolite/porous carbon composites were 676 m²/g and 317 meq/100 g, respectively. Na-A and Na-X zeolites are well-known microporous and hydrophilic materials while carbonized rice husk was found to be mesoporous (pores of ∼3.9 nm) and hydrophobic. These hybrid microporous-mesoporous and hydrophilic-hydrophobic composites are expected to be useful for decontamination of metal cations as well as organic contaminants simultaneously.     

Heterometallic Pt-Ag and Pt2Ag transition metal complexes

Complexes of type {cis-[Pt](μ-σ,π-CCPh)₂}AgX (3a, [Pt] = (bipy′)Pt, X = FBF₃; 3b, [Pt] = (bipy′)Pt, X = FPF₅; 3c, [Pt] = (bipy)Pt, X = OClO₃; 3d, [Pt] = (bipy′)Pt, X = BPh₄; bipy′ = 4,4′-dimethyl-2,2′-bipyridine; bipy = 2,2′-bipyridine) are accessible by combining cis-[Pt](CCPh)₂ (1a, [Pt] = (bipy′)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] (2a, X = BF₄; 2b, X = PF₆; 2c, X = ClO₄; 2d, X = BPh₄). In 3a-3d the platinum(II) and silver(I) ions are connected by σ- and π-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{cis-[Pt](μ-CCPh)₂}₂Ag]X (8a, [Pt] = (bipy)Pt, X = BF₄; 8b, [Pt] = (bipy′)Pt, X = PF₆; 8c, [Pt] = (bipy)Pt, X = BF₄) is produced. The solid state structure of 8a was determined by single X-ray crystal structure analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](CCPh)₂ units. Within this structural arrangement the phenyl acetylides of individual [Pt](CCPh)₂ entities possess a μ-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt → Ag interaction is found (Pt-Ag 2.8965(3) Å). The respective silver carbon distances Ag-C_α (2.548(7), 2.447(7) Å) and Ag-C_β (3.042(7), 2.799(8) Å)(PtC_αC_βPh) confirm this structural motif.Complexes 8a-8c isomerize in solution to form trimetallic [{cis-[Pt](μ-σ,π-CCPh)₂}₂Ag]X (9a, [Pt] = (bipy)Pt, X = BF₄; 9b, [Pt] = (bipy′)Pt, X = PF₆; 9c, [Pt] = (bipy)Pt, X = ClO₄). In the latter molecules the organometallic cation [{cis-[Pt](μ-σ,π- CCPh)₂}₂Ag]⁺ is set-up by two nearly orthogonal positioned [Pt](CCPh)₂ entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhCC units are η²-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.     

Peroxidase-like activity of mesoporous silica encapsulated Pt nanoparticle and its application in colorimetric immunoassay

Nanomaterial-based artificial enzymes have received great attention in recent year due to their potential application in immunoassay techniques. However, such potential is usually limited by poor dispersion stability or low catalytic activity induced by the capping agent essentially required in the synthesis. In an attempt to address these challenges, here, we studied the novel Pt nanoparticles (NPs) based peroxidase-like mimic by encapsulating Pt NP in mesoporous silica (Pt@mSiO₂ NPs). Compared with other nanomaterial-based artificial enzymes, the obtained Pt@mSiO₂ NPs not only exhibit high peroxidase-like activity but also have good dispersion stability in buffer saline solution when grafted with spacer PEG. Results show that when the thickness of silica shell is about 9 nm the resulting Pt@mSiO₂ NPs exhibit the catalytic activity similar to that of Pt NPs, which is approximately 26 times higher than that of Fe₃O₄ NPs (in terms of K_cat for H₂O₂). Due to the protection of silica shell, the subsequent surface modification with antibody has little effect on their catalytic activity. The analytical performance of this system in detecting hCG shows that after 5 min incubation the limit of detection can reach 10 ng mL⁻¹ and dynamic linear working range is 5–200 ng mL⁻¹. Our findings pave the way for design and development of novel artificial enzyme labeling.     

Kinetics and mechanism of electrochemical oxygen reduction using Platinum/clay/Nafion catalyst layer for polymer electrolyte membrane fuel cells

This work demonstrates the use of amino functionalized Mg-phyllosilicate clay/Nafion nanocomposite film embedded with Pt nanoparticles (Pt/AC/N) for catalyzing oxygen reduction reaction (ORR) in sulphuric acid medium. Pt/AC/N nanocomposite films were surface characterized using transmission electron microscope. Cyclic and linear scan voltammetry studies were carried out under hydrodynamic conditions taking rotating-ring disc electrode (RRDE) as the working electrode. The effects of clay content, Pt mass loading, electrode rotation rate, and temperature on the ORR kinetics were studied. The Tafel slopes were found to vary between 118 and 126 mV dec⁻¹ indicating a good ORR kinetics. The exchange current density values calculated after mass transfer correction ranged from 5.8 × 10⁻⁷ to 2.4 × 10⁻⁶ A cm⁻². From the RRDE disc currents, Koutecky-Levich plots were constructed and the ORR mechanism was found to follow a four electron path with minimum H₂O₂ formation of ∼1.6%. The effect of temperature on ORR kinetics was found at 25, 40, and 50 °C. The energy of activation calculated to be 7.68 kJ mol⁻¹ and comparable to the standard Pt/C catalyzed ORR systems.     

Polyfuran/zeolite LTA composites and adsorption properties

Composites of polyfuran (PFu) with LTA type (3A, 4A, 5A) zeolites were prepared via chemical oxidative polymerization of furan (Fu) in the presence of a dispersion of zeolites (powder) in ACN solvent using anhydrous FeCl₃ oxidant at an ambient temperature. The composites were characterized by Fourier transform infrared spectroscopic (FTIR) analysis. FTIR results showed that the composites of 3A zeolite with the smallest pore size did not indicate absorption for benzoyl chloride due to surface structural of OH groups. Thermogravimetric analysis revealed the stability order as: 3A > PFu/3A > PFu, 4A > PFu/4A > PFu, 5A > PFu/5A > PFu. Scanning electron microscopic analysis and X-ray diffraction analysis indicated the formation of polyfuran on zeolite structures. Conductivity values of samples are in the range of semi conductors.     

Fabrication of Pt/polypyrrole hybrid hollow microspheres and their application in electrochemical biosensing towards hydrogen peroxide

Pt/polypyrrole (PPy) hybrid hollow microspheres were successfully prepared by wet chemical method via Fe₃O₄ template and evaluated as electrocatalysts for the reduction of hydrogen peroxide. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), inductive coupled plasma emission spectrum (ICP) and Fourier-transform infrared spectra (FTIR) measurements. The results exhibited that ultra-high-density Pt nanoparticles (NPs) were well deposited on the PPy shell with the mean diameters of around 4.1 nm. Cyclic voltammetry (CV) results demonstrated that Pt/PPy hybrid hollow microspheres, as enzyme-less catalysts, exhibited good electrocatalytic activity towards the reduction of hydrogen peroxide in 0.1 M phosphate buffer solution (pH = 7.0). The composite had a fast response of less than 2 s with linear range of 1.0-8.0 mM and a relatively low detection limit of 1.2 μM (S/N = 3). The sensitivity of the sensor for H₂O₂ was 80.4 mA M⁻¹ cm⁻².     

The effect of acidity behaviour of Y zeolites on the catalytic degradation of polyethylene

Thermogravimetric (TGA) and differential scanning calorimetric (DSC) analyses were used to investigate the effect of the acidity behaviour of Y zeolites on the catalytic degradation of polyethylene (PE). The acidity behaviour of these zeolites was modified by ion exchange treatments. Two Y zeolites with similar Si/Al atomic ratios were subjected to an ion exchange treatment using NaNO₃ for H-form (HY) and NH₄NO₃ for Na-form (NaY). The activity and the deactivation behaviour of the Y zeolites were determined in the samples by TGA measurements, using a polymer/catalyst ratio of 9:1. The sample residues obtained after an isothermic TGA, were analysed by DSC, in order to evaluate the crystallinity of each mixture. The HY zeolite, which has the strongest acidity, reduced the onset temperature resulting in more rapid degradation of the polymer. It is shown that the ion exchange treatment over Y zeolites enhances the selective catalytic degradation of polymer in detriment of the rapid deactivation.     

Synthesis of platinum-iodo-alkyl/aryl complexes in ligand-exchange reactions: Determination of the structure of Pt{(S,S)-bdpp}(X)I complexes (X = Me, I) by X-ray crystallography

Pt{(S,S)-bdpp}(R)I (bdpp = 2,4-bis(diphenylphosphino)pentane; R = Me, Ph, Bz, 2-Tioph) complexes were formed in alkyl/aryl ligand - iodide ligand-exchange reactions by reacting the corresponding Pt{(S,S)-bdpp}R₂ complexes with methyl iodide. The Pt{(S,S)-bdpp}(Me)I complex was isolated and fully characterised. The influence of the X ligand on the platinum-bdpp chelate conformation was investigated in Pt{(S,S)-bdpp}(X)I (X = I, SnCl₃, Me) complex series by means of X-ray crystallography.     

SnMe3/Pt/HY分子筛的合成与表征

在高真空系统下研究了SnMe4与Pt修饰的HY沸石分子筛表面的接枝反应,并用元素分析、FT-IR,XRD,DRS,BET,GC等表征了接枝产物的组成和性质。结果表明：Pt／HY沸石的表面羟基可以与SnMe4在常温下反应,将三甲基锡基团接枝在沸石的超笼中。Pt／HY与SnMe4发生接枝反应后晶相结构没有改变,微孔体积和BET表面积都下降。     

Heterogeneous bimetallic Pt-Sn/γ-Al2O3 catalyzed direct synthesis of diamines from N-alkylation of amines with diols through a borrowing hydrogen strategy

Direct synthesis of diamines has been efficiently realized from the N-alkylation of amines with diols by means of heterogeneous bimetallic Pt-Sn/γ-Al₂O₃ catalyst (0.5 wt % Pt, molar ratio Pt:Sn = 1:3) through a ‘Borrowing Hydrogen’ strategy under ligand-free conditions. The present methodology provides an environmentally benign route to diamines.     

The reaction of the group-13 alkyls ER3 (E = Al, Ga, In; R = CH2t-Bu, CH2 SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH2t-Bu)]

The reactions of the sterically demanding group-13 alkyls ER₃ (E = Al, Ga, In; R = CH₂t-Bu, CH₂SiMe₃) with the platinum-complex [(dcpe)Pt(H)(CH₂t-Bu)] were re-investigated. The bimetallic compounds [(dcpe)Pt(ER₂)(R)] (3: E = Ga, R = CH₂SiMe₃; 5: E = In, R = CH₂t-Bu; dcpe = bis(dicyclohexylphosphino)ethane) with direct σ(Pt-E) bonds were obtained by oxidative addition of an E-C bond to the coordinatively unsaturated fragment [(dcpe)Pt] produced in situ by thermolysis of the starting complex [(dcpe)Pt(CH₂t-Bu)(H)]. The single crystal structure determination reveals a Pt-Ga bond length of 2.376(2) Å and a Pt-In bond length of 2.608(1) Å. All new compounds were characterised by elemental analysis, ³¹P and ¹⁹⁵Pt NMR spectroscopy. Interestingly, the Pt-Ga compound 3 slowly transforms into the platinum alkyl/hydride isomer {(dcpe)Pt(μ₂-H)[CH₂Si(CH₃)₂ CH₂Ga(CH₂SiMe₃)₂]} (4) during crystallization from solution at room temperature. The X-ray single crystal structure analysis revealed both complexes 3 and 4 coexisting in the unit cell in a 1:1 relation. The inaccessibility of analytically pure samples of the Pt-Al complex {(dcpe)Pt[Al(CH₂t-Bu)₂](CH₂t-Bu)} (6), postulated as intermediate of the reaction of [(dcpe)Pt(H)(CH₂t-Bu)] with Al(CH₂t-Bu) on the basis of ³¹P and ¹⁹⁵Pt NMR data, is attributed to an enhanced tendency to isomerisation into the alkyl/hydride Pt/Al congener of 4. A brief DFT analysis of the bonding situation of the model complex [(dhpe)Pt(GaMe₂)(Me)] (1M) revealed, that the contribution of π(Pt-Ga) back-bonding is negligible.     

Pt/porous-IrO2 nanocomposite as promising electrocatalyst for unitized regenerative fuel cell

Pt/porous-IrO₂ composite as bifunctional oxygen electrocatalyst for unitized regenerative fuel cell has been prepared by chemical reduction of Pt on porous IrO₂ which is obtained via template-removal method. X-ray diffraction and transmission electron microscopy characterizations indicate that the Pt nanoparticles (ca. 4.4 nm) are deposited on both internal and external sites of porous IrO₂ nanoparticles. Electrochemical analyses show that the activity toward oxygen evolution reaction on Pt/porous-IrO₂ catalyst is 28% (at 1.55 V) higher than that on Pt/commercial-IrO₂ catalyst, and the activity towards oxygen reduction reaction on the former is 2.3 times (at 0.85 V) that on the latter. Oxygen reduction on Pt/porous-IrO₂ catalyst follows the first-order kinetics and the four-electron mechanism.     

Mechanistic investigation of the thermal decomposition of Biphen(OPi-Pr)PtEt2: An entrance into C-C single bond activation?

Biphen(OPi-Pr) and (COD)PtCl₂ give Biphen(OPi-Pr)PtCl₂ which upon treating with ethyl Grignard forms Biphen(OPi-Pr)PtEt₂. The thermal decomposition of Biphen(OPi-Pr)PtEt₂ was investigated in the temperature range of 353-383 K. The clean and quantitative formation of the Pt(Ethene) adduct was observed. X-ray structures of a molecule in the solid state of all three reaction products and two further related complexes with phenyl fingers instead of i-Pr have been determined. For the complexes with i-Pr fingers a decisive deviation from a square plane is observed in contrast to the complexes with phenyl fingers. The P-Pt-P angle increases from about 95° in Biphen(OPi-Pr)PtCl₂ to about 120° in Biphen(OPi-Pr)Pt(Ethene), forcing the bridging C-C single bond of the biphenyl fragment as near as 4.17 Å to the Pt center. No through-space coupling between the bridging C atoms and the Pt center could be observed in ¹³C NMR spectroscopy. No bond lengthening of the bridging C-C single bond in the biphenyl fragment was observed in Biphen(OPi-Pr)Pt(Ethene) in comparison to the precursor complexes. The thermal decomposition of Biphen(OPi-Pr)PtEt₂ can be described by a first-order kinetic and the activation parameters were determined (temperature range: 353-383 K; ΔH^‡ = 173.8 ± 16.2 kJ/mol and ΔS^‡ = 104.7 ± 44.1 J/(mol K)). The reaction kinetics were also measured for perdeuterated ethyl groups yielding in a kinetic isotopic effect of 1.56 ± 0.14 which was almost temperature-independent. Selective deuteration at α and β position of the ethyl group, respectively, showed that β-H elimination takes place fast in comparison to the complete thermolysis. In the temperature range of 333-353 K only a scrambling of the deuterium atoms was found without further decomposition (temperature range: 333-353 K; Δ_scramH^‡ = 76.1 ± 15.2 kJ/mol, Δ_scramS^‡ = −80.7 ± 45.5 J/(mol K) for Biphen(OPi-Pr)PtEt₂-d⁶). The ethene is not lost during the scrambling process. The scrambling process is connected with a primary KIE decisively larger than 1.56. Biphen(OPi-Pr)Pt(Ethene) exchanges the coordinated ethene with ethene in solution as proven by labeling experiments. Both a dissociative and an associative mechanism could be shown to take place as ethene exchange reaction by means of VT¹H NMR spectroscopy via line shape analysis (temperature range: 333-373 K; Δ_assH^‡ = 26.9 ± 29.6 kJ/mol, Δ_assS^‡ = −148.0 ± 87.5 J/(mol K), Δ_dissH^‡ = 86.0 ± 6.5 kJ/mol, Δ_dissS^‡ = 5.4 ± 17.8 J/(mol K)). The Pt(0) complex formed during the dissociative loss of ethene activates several substrates among them: O₂, H₂, H₂SiPh₂ via Si-H activation, MeI presumably via forming a cationic methyl adduct and ethane via C-H activation but it was proven that the bridging C-C single bond of the biphenyl fragment is not even temporarily broken. The materials were characterized by means of ¹H NMR, ¹³C NMR, ³¹P NMR, ¹⁹⁵Pt NMR, EA, MS, IR, X-ray analysis and polarimetric measurement where necessary.     

Insertion of tin(II) bromide into Pt–X (X = Cl,Br) bond of dimethylplatinum(IV) complexes: A novel polymorphic form of [PtBr2(bpy)]

The platinum(II) complex [PtMe₂(bpy)] (bpy = 2,2′-bipyridine) reacted with a large excess of dihaloalkanes X(CH₂)_nX (n = 1, X = Cl; n = 4, X = Br) to form the platinum(IV) complexes [PtMe₂X{(CH₂)_nX}(bpy)] (n = 1, X = Cl, 1a; n = 4, X = Br, 1b). The reaction of complexes 1a and 1b with SnBr₂ resulted in insertion of SnBr₂ into Pt–X (X = Cl, Br) bond to afford the trihalostannyl complexes [PtMe₂(SnBr₂X){(CH₂)_nX}(bpy)] (n = 1, X = Cl, 2a; n = 4, X = Br, 2b). The synthesis of such trihalostannylplatinum(IV) complexes is reported for the first time. The complex 2a was decomposed in CH₂Cl₂ solution and single crystals of [PtBr₂(bpy)] (3a) were obtained. The X-ray structure determination of 3a revealed a new polymorphic form of [PtBr₂(bpy)]. The molecules undergo a remarkable stacking along the b-axis to form a zigzag Pt?Pt?Pt chain containing both short (3.799 Å) and long (5.175 Å) Pt?Pt separations through the crystal. The crystal structure is compared to that of the yellow modification of [PtBr₂(bpy)].     

Effect of monomer molecular flow on electrode surface on the structure of poly(α-tetrathiophene) obtained by anodic polymerization

Different structures have been found for poly(α-tetrathiophene) [poly(α-4TF)] electrosynthesized on Pt by anodic oxidation of 1.0 mM monomer solutions in media such as 45:35:20 (v/v/v) acetonitrile/THF/DMF, 45:35:20 (v/v/v) acetonitrile/ethanol/DMF and 72:28 (v/v) acetonitrile/DMF containing 0.1 M LiClO₄; as well as 72:28 (v/v) acetonitrile/DMF with 0.1 M NaClO₃, under dynamic and static conditions at 25 °C. In all cases the polymer was generated by chronoamperometry at 1.000 V vs. Ag∣AgCl, corresponding to the first oxidation peak detected by cyclic voltammetry. Uniform, adherent, insoluble and black polymer films were obtained under these conditions. The resulting structures have been elucidated by combining the information of their IR spectrum, n_ox-value and doping level of the counterion. The degree of crosslinking of every polymer has been quantified and related to the molecular flow of monomer on the Pt electrode. A monomer concentration flow between 4 × 10⁻⁶ and 5 × 10⁻⁶ mmol cm⁻² s⁻¹ was determined as the limiting value below which the polymer grows with crosslinking. This value corresponds to the electropolymerization rate of α-4TF by Pt area unit at 25 °C.     

Oxidative addition of (PhSe)2 and (FcSe)2 to zerovalent palladium and platinum trialkylphosphine complexes (Fc = ferrocenyl, [Fe(η-C5H5)(η-C5H4)])

Room temperature reaction of [Pd₂(dba)₃]/PR₃ or [Pt(C₂H₄)(PR₃)₂] (dba = dibenzylideneacetone; R = Et, Bu) with the diselenides (R′Se)₂ (R′ = Ph, Fc) yielded the oxidative addition products trans-[M(SeR′)₂(PR₃)₂] (M = Pd, Pt). These have been characterised by multinuclear NMR and UV-Vis spectroscopy, mass spectrometry, and, in the cases of trans-[Pt(SePh)₂(PR₃)₂] (R = Et, Bu) and trans-[Pt(SeFc)₂(PBu₃)₂], also by X-ray crystallography.     

Preparation of silica-PS composite particles and their application in PET

To investigate how the superfine particles disperse in the polymers, the paper presented the preparation of monodisperse silica particles by Stöber method, and then grafted by γ-methacrylic propyl trimethoxysilane (MPS) as a coupling agent. Using these modified particles, the more stable silica-PS superfine composite particles with higher monodispersity than these of previous reports are prepared and reported through dispersion polymerization (DP) method, whose morphology is investigated with transmission electron microscope (TEM). Their high stability is provided from the bonding of CC groups of MPS to the silanol groups on the surface of silica particles from FTIR.Using this DP process, the influence of different size grafted silica particles on the morphology, polystyrene (PS) encapsulation behavior and the distribution in these composite particles have been investigated. When the grafted silica size is in nanoscale or less than 54 nm, the spherical shape of neither silica particles nor their composite particles is regular, but they can homogeneously disperse in polystyrene. As the size (d_n) of grafted silica particles increase to submicrometer (or 100 nm < d_n < 1000 nm), their coefficient variance of size distribution (C_v) ranges from only 9.0% to 1.5%. These obtained particles are completely encapsulated by PS with more regular shape, and have their C_v below 7%. When the size of silica particles reaches 380 nm, their C_v obviously reduces to 2.5%, and specially, the number of grafted silica particles approaches to one in each of the composite particles. But, when the silica size reaches 602 nm, PS can hardly encapsulate grafted silica particles and free silica particles appear in reactive system.Furthermore, using the silica particles of 380 nm, a series of core-shell structured superfine composite particles of 640-1100 nm with C_v lower than 11% are obtained. Under the set conditions, the preparing factors on these composite particles using 380 nm grafted silica particles is discussed, and the best reaction condition for the well-dispersed and regular periphery silica-PS composite particles is optimized as, the additions amounts of PVP, styrene, AIBN, grafted SiO₂ and H₂O are 0.23 mmol L⁻¹, 0.60 mol L⁻¹, 6.10 mmol L⁻¹, 0.10 mol L⁻¹ and 5.50 mL, respectively. Under this case, the composite particles can be prepared with C_v below 8%.At last, these composite particles are mixed with poly(ethylene terephthalate) (PET) to investigate their nucleation effect. Results show that all different size particles can promote PET’s crystallization and enhance the crystallization rate, and PET’s crystallization temperature (T_mc) is obviously enhanced from 193 to 205 °C through differential scanning calorimetry (DSC). It is strongly suggested that different silica size level all play nucleation role in PET, and thus explain the nucleation effect of multiscale inorganic particles.