Theoretical Studies on the Reaction Mechanism of Platinum-Catalyzed Diboration of Allenes

The reaction mechanism of Pt(0)-catalyzed diboration reaction of allenes is investigated by the density functional method B3LYP. The overall reaction mechanism is examined. The electronic mechanisms of the allene insertion into the Pt-B bond are discussed in terms of the electron donation, back-donation, and d-pi interaction. During allene insertion into the Pt-B bond, the internal carbon atom of allene is preferred over the terminal one due to the stronger electron back-donation and stronger charge transfer in the former case than that in the latter one.

Electrostatic layer-by-layer a of platinum-loaded multiwall carbon nanotube multilayer: A tunable catalyst film for anodic methanol oxidation

A simple layer-by-layer (LBL) electrostatic adsorption technique was developed for deposition of films composed of alternating layers of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged multiwall carbon nanotubes bearing platinum nanoparticles (Pt-CNTs). PDDA/Pt-CNT film structure and morphology up to six layers were characterized by scanning electron microscopy and ultraviolet-visible spectroscopy, showing the Pt-CNT layers to be porous and uniformly deposited within the multilayer films.

Platinum-macrocycle co-catalysts for electro-oxidation of formic acid

In this paper, it was found that the electrocatalytic activity of a Pt electrode for the electro-oxidation of formic acid could be dramatically enhanced with the modification of macrocycle compounds, such as iron-tetrasulfophthalocyanine (FeTSPc). The electro-oxidation of formic acid on a modified Pt electrode with FeTSPc occurs mainly through a direct pathway. A series of macrocycle compounds were also investigated as modifiers and exhibited a promotion effect similar to the Pt electrode.

Synthesis and characterization of Prussian blue@platinum nanoparticle hybrids from a mixture solution of platinum nanocatalyst and ferric ferricyanide

In the present study, platinum nanoparticles modified with Prussian blue (PB) have been synthesized by a heterogeneous catalytic reaction. Transmission electronic microscopy (TEM) confirmed the deposition of nanoclusters around the Surfaces of platinum particles, and spectroscopic studies verified that the molecular composition of the nanoclusters was dominantly PB and a minority of platinum ferricyanide. Thus, it was shown that the platinum particles behaved not only as catalysts for the growth of PB, but also as a reactant to generate a PB analogue complex.

Surface potential images of polycrystalline organic semiconductors obtained by Kelvin probe force microscopy

P-type copper phthalocyanine (CuPc) and n-type hexadecafluorophthalocyanina-tocopper (F16CuPc) polycrystalline films were investigated by Kelvin probe force microscopy (KPFM). Topographic and corresponding surface potential images are obtained simultaneously. Surface potential images are related with the local work function of crystalline facets and potential barriers at the grain boundaries (GBs) in organic semiconductors. Based on the spatial distribution of surface potential at GBs, donor- and acceptor-like trapping states in the grain boundaries (GBs) of p-CuPc and n-F16CuPc films are confirmed respectively.

Electrodeposition of platinum nanoclusters on type I collagen modified electrode and its electrocatalytic activity for methanol oxidation

We firstly reported a novel polymer matrix fabricated by type I collagen and polymers, and this matrix can be used as nanoreactors for electrodepositing platinum nanoclusters (PNCs). The type I collagen film has a significant effect on the growth of PNCs. The size of the platinum nanoparticles could be readily tuned by adjusting deposition time, potential and the concentration of electrolyte, which have been verified by field-emitted scanning electron microscopy (FE-SEM). Furthermore, cyclic voltammetry (CV) has demonstrated that the as-prepared PNCs can catalyze methanol directly with higher activity than that prepared on PSS/PDDA film, and with better tolerance to poisoning than the commercial E-TEK catalyst. The collagen-polymer matrix can be used as a general reactor to electrodeposit other metal nanostructures.

Green synthesis of highly stable platinum nanoparticles stabilized by amino-terminated ionic liquid and its electrocatalysts for dioxygen reduction and methanol oxidation

Preparation of monodispersed platinum nanoparticles with average size 2.0 nm stabilized by amino-terminated ionic liquid was demonstrated. The resulting platinum nanoparticles (Pt-IL) retained long-term stability without special protection. The Pt-IL nanoparticles exhibited high electrocatalytic activity toward reduction of oxygen and oxidation of methanol. Rotating disk electrode voltammetry and rotating ring-disk electrode voltammetry confirmed that the Pt-IL films could catalyze an almost four-electron reduction of dioxygen to water.

Synthesis, characterization and electrophosphorescent properties of mononuclear platinum(II) complexes based on 2-phenylbenzoimidazole derivatives

The rational design, synthesis and characterization of five phosphorescent platinum complexes [(C boolean AND N) Pt(acac)] [Hacac = acetylacetone, HC boolean AND N = 1-methyl-2-(4-fluorophenyl)benzoimidazole (H-FMBI), 1-methyl-2-phenylbenzoimidazole (H-MBI), 1,2-diphenyl-benzoimidazole (H-PBI), 1-(4-(3,6-di-t-butylcarbazol-9-yl)) phenyl-2-phenylbenzoimidazole (t-BuCz-H-PBI), and 1-(4-(3,6-di-(3,6-di-t-butyl-carbazol-9-yl))carbazol-9-yl) phenyl-2-phenylbenzoimidazole (t-BuCzCz-H-PBI)] have been discussed. The crystal structure of (MBI) Pt(acac) shows a nearly ideal square planar geometry around Pt atom and the weak intermolecular interactions with pi-pi spacing of 3.55 angstrom. All of the complexes emit green phosphorescence from the metal-to-ligand charge-transfer (MLCT) excited state with high quantum efficiency (0.08-0.17) at room temperature.

Synthesis of polycrystalline nanotubular Bi2Te3

Polycrystalline nanotubular Bi2Te3 could be prepared via a high-temperature solution process using nanoscale tellurium, decomposed from trioctylphosphine oxide (TOPO) extracted tellurium species (Te-TOPO), as sacrificial template. The formation of such tubular structure is believed to be the result of outward diffusion of Te during the alloying process. The electrical properties (Seebeck coefficient and electrical conductivity) of the polycrystalline nanotubular Bi2Te3 have been studied and the experimental results show that the electrical conductivity is approximately three orders of magnitude smaller than bulk bismuth telluride materials mainly due to the much larger resistance brought by the insufficient contact between the nanotubular structures.

Synthesis, characterization, photophysics and electrophosphorescent applications of phosphorescent platinum cyclometalated complexes with 9-arylcarbazole moieties

A series of cyclometalating platinum(II) complexes with substituted 9-arylcarbazolyl chromophores have been synthesized and characterized. These complexes are thermally stable and most of them have been characterized by X-ray crystallography. The phosphorescence emissions of the complexes are dominated by (MLCT)-M-3 excited states. The excited state properties of these complexes can be modulated by varying the electronic characteristics of the cyclometalating ligands via substituent effects, thus allowing the emission to be tuned from bright green to yellow, orange and red light. The correlation between the functional properties of these metallophosphors and the results of density functional theory calculations was made. Because of the propensity of the electron-rich carbazolyl group to facilitate hole injection/transport, the presence of such moiety can increase the highest occupied molecular orbital levels and improve the charge balance in the resulting complexes relative to the parent platinum(II) phosphor with 2-phenylpyridine ligand.

Efficient Electrophosphorescence from a Platinum Metallopolyyne Featuring a 2,7-Carbazole Chromophore

The synthesis, thermal and emission properties of an electrophosphorescent platinum(II) metallopolyyne polymer consisting of 9-butylcarbazole-2,7-diyl spacer P1 are described. The optical and electronic properties of P1 are compared to their molecular diplatinum(II) and digold(I) model complexes. The photophysical properties of P1 are somehow analogous to its 2,7-fluorene-linked congener but differs significantly from that for the 3,6-carbazole derivative. Its optical band gap is notably reduced as compared to that for the 3,6-carbazole analog. Multi-layer polymer light-emitting diodes (PLEDs) were fabricated with P1 as the emitting layer which gave a strong green-yellow electrophosphorescence. The best PLED can reach the maximum current efficiency of 4.7 cd . A(-1) at 5 wt.-% doping level, corresponding to an external quantum efficiency of 1.5%. This represents the first literature example of efficient PLEDs exhibiting pure triplet emission under electrical excitation for metallopolyynes without the concomitant singlet emission.

Nanocomposite based on depositing platinum nanostructure onto carbon nanotubes through a one-pot, facile synthesis method for amperometric sensing

Platinum nanoparticles (Pt NPs) were deposited onto multi-walled carbon nanotubes (MWNTs) through direct chemical reduction without any other stabilizing agents. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry were employed to characterize the morphology of the as-prepared nanocomposite (noted as Pt NPs-MWNTs) and further identify the Pt NPs on the surface of MWNTs. The nanocomposite demonstrated the ability to electrocatalyze the oxidation of hydrogen peroxide and substantially raises the response current. A sensitivity of 591.33 mu A mM(-1) cm(-2) was obtained at Pt NPs-MWNTs modified electrode. Thus, we immobilized glucose oxidase (GOD) as a model enzyme on the nanocomposite-based electrode with a thin layer of Nafion to fabricate a glucose biosensor, which showed sensitive and fast response to glucose. The influence of the GOD loading was investigated and the biosensor with an enzyme loading concentration of 10 mg/mL shows optimal performance for glucose detection, that is, a detection limit of 3 mu M and a response time of 3 s, respectively.

Polyethylene glycol-stabilized platinum nanoparticles: The efficient and recyclable catalysts for selective hydrogenation of o-chloronitrobenzene to o-chloroaniline

In the present work, platinum nanoparticles were prepared by in situ reduction with polyethylene glycols (PEGs). The catalytic performance of Pt nanoparticles immobilized in PEGs (Pt-PEGs) is discussed for the hydrogenation of o-chloronitrobenzene (o-CNB). A high selectivity to o-chloroaniline (o-CAN) of about 99.7% was obtained with the Pt-PEGs catalysts at the complete conversion of o-CNB, which is much higher than that (83.4%) obtained over the conventional catalyst of Pt/C. The Pt nanoparticies could be immobilized in PEGs stably and recycled for four times with the same activity and selectivity. It presents a promising performance in the hydrogenation and its wide application in catalytic reactions is expected.

A versatile color tuning strategy for iridium(III) and platinum(II) electrophosphors by shifting the charge-transfer states with an electron-deficient core

By fusing an electron-deficient ring system with the phenyl ring of a 2-phenylpyridine (ppy)-type ligand, a new and synthetically versatile strategy for the phosphorescence color tuning of cyclometalated iridium(III) and platinum(II) metallophosphors has been established. Two robust red electrophosphors with enhanced electron-injection/electron-transporting features were prepared by using an electron-trapping fluoren-9-one chromophore in the ligand design. The thermal, photophysical, redox and electrophosphorescent properties of these complexes are reported. These exciting results can be attributed to a switch of the metal-to-ligand charge-transfer (MLCT) character of the transition from the pyridyl groups in the traditional Ir-III or Pt-II ppy-type complexes to the electron-deficient ring core, and the spectral assignments corroborate well with the electrochemical data as well as the timedependent density functional theory (TD-DFT) calculations. The electron-withdrawing character of the fused ring results in much more stable MLCT states, inducing a substantial red-shift of the triplet emission energy from yellow to red for the Ir-III complex and even green to red for the PtII counterpart.

Polyethyleneimine-Functionalized Platinum Nanoparticles with High Electrochemiluminescence Activity and Their Applications to Amplified Analysis of Biomolecules

Polyethyleneimine-functionalized platinum nanoparticles (PtNPs) with excellent electrochemiluminescence (ECL) properties were synthesized and applied to the amplified analysis of biomolecules. These particles were prepared at room temperature, with hyperbranched polyethyleneimine (HBPEI) as the stabilizer. The UV/Vis absorption spectra and transmission electron microscopy images clearly confirmed the formation of monodisperse PtNPs. Such particles proved to possess high stability against salt-induced aggregation, enabling them to be employed even under high-salt conditions. Owing to the existence of many tertiary amine groups, these particles exhibited excellent ECL behavior in the presence of tris(2.2'-bipyridyl)ruthenium(II). An HBPEI-coated particle possessed an ECL activity that was at least 60 times higher than that of a tripropylamine molecule. Furthermore, these particles could be immobilized on the 3-aminopropyltriethoxysilane-treated quartz substrates to amplify the binding sites for carboxyl groups. Through this approach, PtNPs were applied to the amplified analysis of the hemin/G-quadruplex DNAzyme by using the luminol/H2O2 chemiluminescence method.