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Full-Text Articles in Physics

Pore Diameter Dependence Of Catalytic Activity: P-Nitrobenzaldehyde Conversion To An Aldol Product In Amine-Functionalized Mesoporous Silica, Andres Garcia, Igor I. Slowing, James W. Evans Jul 2018

Pore Diameter Dependence Of Catalytic Activity: P-Nitrobenzaldehyde Conversion To An Aldol Product In Amine-Functionalized Mesoporous Silica, Andres Garcia, Igor I. Slowing, James W. Evans

Chemistry Publications

The reaction yield for conversion of p-nitrobenzaldehyde (PNB) to an aldol product in amine-functionalized mesoporous silica nanoparticles (MSN) exhibits a 20-fold enhancement for a modest increase in pore diameter, d. This enhanced catalytic activity is shown to reflect a strong increase in the “passing propensity,” 𝒫, of reactant and product species inside the pores. We find that 𝒫 ≈ 0, corresponding to single-file diffusion, applies for the smallest d which still significantly exceeds the linear dimensions of PNB and the aldol product. However, in this regime of narrow pores, these elongated species must align with each other and with the pore ...


A Molecular Debye-Hückel Theory Of Solvation In Polar Fluids: An Extension Of The Born Model, Tiejun Xiao, Xueyu Song Dec 2017

A Molecular Debye-Hückel Theory Of Solvation In Polar Fluids: An Extension Of The Born Model, Tiejun Xiao, Xueyu Song

Ames Laboratory Accepted Manuscripts

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated in ...


A Molecular Debye-Hückel Theory And Its Applications To Electrolyte Solutions: The Size Asymmetric Case, Tiejen Xiao, Xueyu Song Mar 2017

A Molecular Debye-Hückel Theory And Its Applications To Electrolyte Solutions: The Size Asymmetric Case, Tiejen Xiao, Xueyu Song

Chemistry Publications

A molecular Debye-Hückel theory for electrolyte solutions with size asymmetry is developed, where the dielectric response of an electrolyte solution is described by a linear combination of Debye-Hückel-like response modes. As the size asymmetry of an electrolyte solution leads to a charge imbalanced border zone around a solute, the dielectric response to the solute is characterized by two types of charge sources, namely, a bare solute charge and a charge distribution due to size asymmetry. These two kinds of charge sources are screened by the solvent differently, our theory presents a method to calculate the mean electric potential as well ...


Electrostatic Correlations At The Stern Layer: Physics Or Chemistry?, Alex Travesset Jan 2009

Electrostatic Correlations At The Stern Layer: Physics Or Chemistry?, Alex Travesset

Physics and Astronomy Publications

We introduce a minimal free energy describing the interaction of charged groups and counterions including both classical electrostatic and specific interactions. The predictions of the model are compared against the standard model for describing ions next to charged interfaces, consisting of Poisson–Boltzmann theory with additional constants describing ion binding, which are specific to the counterion and the interfacial charge (“chemical binding”). It is shown that the “chemical” model can be appropriately described by an underlying “physical” model over several decades in concentration, but the extracted binding constants are not uniquely defined, as they differ depending on the particular observable ...