Why the abnormal phenomena of D-band center theory exist?A new BASED theory for surface catalysis and chemistry

Since the D-band center theory was proposed,it has been widely used in the fields of surface chemistry by almost all researchers,due to its easy understanding,convenient operation and relative accuracy.However,with the continuous development of material systems and modification strategies,researchers have gradually found that D-band center theory is usually effective for large metal particle systems,but for small metal particle systems or semiconductors,such as single atom systems,the opposite conclusion to the D-band center theory is often obtained.To solve the issue above,here we propose a bonding and anti-bonding orbitals stable electron intensity difference(BASED)theory for surface chemistry.The newly-proposed BASED theory can not only successfully explain the abnormal phenomena of D-band center theory,but also exhibits a higher accuracy for prediction of adsorption energy and bond length of intermediates on active sites.Importantly,a new phenomenon of the spin transition state in the adsorption process is observed based on the BASED theory,where the active center atom usually yields an unstable high spin transition state to enhance its adsorption capability in the adsorption process of intermediates when their distance is about 2.5Å.In short,the BASED theory can be considered as a general principle to understand catalytic mechanism of intermediates on surfaces.

A Negative Donor D^- in a Magnetic Field

Using the method of numerical matrix diagonalization within the effective-mass approximation, we investigated a D^--center quantum dot system subjected to a Gaussian potential confinement. We obtain the dependence of binding energies of the ground-states of the D^--center on the depth of Gaussian potential and the magnetic field strength. The result shows clearly that the binding energies of the ground-states of the D^--center are rather sensitive to the depth of potential and the strength of magnetic field.

Boosting fuel cell catalysis by surface doping of W on Pd nanocubes

The development of active and durable non-Pt electrocatalysts with well-defined microstructure is of great importance to both fuel cell applications and fundamental understanding.Herein,we report a surface-doping process to prepare well-defined W-doped Pd nanocubes with a tunable atomic percent of W from 0 to 1.5%by using the Pd nanocubes as seeds.The obtained 1.2%W-doped Pd nanocubes/C exhibited greatly enhanced electrocatalytic performance toward oxygen reduction reaction in alkaline media,presenting an enhancement factor of 4.7 in specific activity and 2.5 in mass activity compared to the activity of a commercial Pt/C catalyst.The downshift of the d-band center due to a negative charge transfer from W to Pd intrinsically accounts for such improvement in activity by weakening the adsorption of reaction intermediates.Also,the 1.2%W-doped Pd nanocubes/C showed superior catalytic properties for the ethanol oxidation reaction,showing great potential for serving as a bifunctional electrocatalyst in fuel cells.

MULTIPLE CENTER d-β ORBITALS AND CHARGE TRANSFER OF HETERONUCLEAR COUSTERS WITH CUBANE TYPE (Mo_3S_4)_xM^n+ (x=1, 2, M = Cu, W, Ni, Sb. Mo, Sn, Cu_2; n = 4,8)

In this work, with the analysis on MO and electronic structure for a series of heteronuclear cluster with cubane type (Mo4S1 )xMn1(x=1.2. M = Cu, W, Ni, Sb, Mo, Sn, Cu2) we found that it is with the multiple center d-pir orbitals that the ligand Mo3S44+ bonds to the M atom to form these class clusters. It is revealed that the charges transfer from the M atom to Mo atom of the ligand Mo3S44+ and its relationship with the MC (multiple center) d-pπ orbitals. Based on the charge transfer the electronic spectrum and the magnetic property of some cubane clusters have been discussed.

Effects of phospholipase D on cardiopulmonary bypass-induced neutrophil priming

Objective:To investigate the relationship betwe en phospholipase D (PLD) activation and neutrophil priming induced by cardiopulm onary bypass (CPB), and try to clarify whether CPB-induced systemic inflammator y response can be attenuated by inhibiting neutrophilic PLD activation. Methods:Neutrophils were isolated from arterial blood of 8 pat ients undergoing valve replacement before operation and 30 min after initiation of CPB respectively. Both the preoperative and CPB-stirred neutrophils were sub divided into 5 groups by receiving different experimental interventions: (1) bac terial lipopolysaccharide (LPS, 10 ng·ml -1 ), (2) N-formylmethionylph enylalanine (fMLP, 1 μmol·L -1 ), (3) LPS+fMLP, (4) 1-butanol ( 0.5 %)+ LPS+fMLP, (5) vehicle. Elastase and myeloperoxidase (MPO) release was measured f or the parameters of neutrophil activation, neutrophil PLD activity was determin ed by quantitation of choline produced from the stable product of phosphatidylch oline catalyzed by PLD. Results:(1) Preoperative neutrophils treated with LPS+fMLP pre sented significantly higher PLD activity ( 13.48 ± 2.61 nmol choline·h -1 ·mg -1 ) and released more elastase and MPO than cells treated with v ehicle (PLD activity 3.70 ± 0.49 nmol choline·h -1 ·mg -1 , P< 0.01 ), LPS (P< 0.01 ) and fMLP respectively. In 1-butanol+LPS+fMLP group, PLD activity of preoperative neutrop hils was lower than that in LPS+fMLP group (P< 0.01 ), b esides the release of elastase and MPO decreased sharply below both LPS + fMLP a nd fMLP groups (P< 0.01 ). In LPS group, PLD activity wa s higher (P< 0.01 ), while elastase and MPO release did not differ from control. fMLP group presented PLD activity, elastase and MPO rel ease higher than control (P< 0.01 ); nevertheless, lower than LPS+fMLP group (P< 0.01 ). (2) CPB-stirred neutro phils presented prominent PLD activity increment, and even the control level was 3.59 -fold of the pre-operative control (P< 0.01 ) . PLD activity in LPS+fMLP group was higher than that in other groups. Notably, PLD activity was even nonstatistically lower in 1-butanol+LPS+fMLP group than t hat in LPS or fMLP group. CPB-stirred neutrophils in LPS+fMLP group released mo re elastase and MPO than control, LPS, and 1-butanol+LPS+fMLP groups did ( P< 0.01 ); however, neither of the release was statistically different from that of fMLP group. Conclusions:Cardiopulmonary bypass enables neutrophil priming accompanied with significant increase in PLD activity. Inhibition of neutrophil PLD activation attenuates its priming and may alleviate CPB-induced systemic in flammatory reaction.