Modified BET theory for actual surfaces: implementation of surface curvature.

The Brauner-Emmett-Teller (BET) theory was originally based on adsorbing surfaces of zero curvature. The theory is elaborated to include a curvature parameter. The theory has been developed for mono-size dense particles (spherical or rod-like) and porous materials with a sharp pore size distribution (spherical or cylindrical pores). Validation was performed considering 62 relevant published results. It is shown that for porous materials with cylindrical pores (15 cases), while the average error in the calculation of the specific surface area using the original BET theory is ca. 46%, that from the modified theory is ca. 11%. For porous materials with spherical pores (20 cases), an average error of 58% (BET theory) is reduced to 15%. To apply the new theory to dense materials, in addition to the probe-gas adsorption isotherm, skeletal density is needed. For meso-porous materials, the curvature parameter is calculated using the BJH theory.

Preparation and characterization of nano-galvanic bimetallic Fe/Sn nanoparticles deposited on talc and its enhanced performance in Cr(VI) removal.

In this study, talc-supported nano-galvanic Sn doped nZVI (Talc-nZVI/Sn) bimetallic particles were successfully synthesized and utilized for Cr(VI) remediation. Talc-nZVI/Sn nanoparticles were characterized by FESEM, EDS, FTIR, XRD, zeta potential, and BET analysis. The findings verified the uniform dispersion of nZVI/Sn spherical nanoparticles on talc surface with a size of 30-200 nm, and highest specific surface area of 146.38 m2/g. The formation of numerous nano-galvanic cells between nZVI core and Sn shell enhanced the potential of bimetallic particles in Cr(VI) mitigation. Moreover, batch experiments were carried out to investigate optimum conditions for Cr(VI) elimination and total Cr(VI) removal was achieved in 20 min using Sn/Fe mass ratio of 6/1, the adsorbent dosage of 2 g/L, initial Cr(VI) concentration of 80 mg/L, at the acidic environment (pH = 5) and temperature of 303 K. Besides, co-existing of metallic cations turned out to facilitate the electron transfer from the nano-galvanic couple of NZVI/Sn, and suggested the revolution of bimetallic particles to trimetallic composites. The aging study of the nanocomposite confirmed its constant high activity during 60 days. The removal reaction was well described by the pseudo-second-order kinetic and the modified Langmuir isotherm models. Overall, due to the synergistic galvanic cell effect of nZVI/Sn nanoparticles and full coverage of active sites by Sn layer, Talc-nZVI/6Sn was utilized as a promising nanocomposite for fast and highly efficient Cr(VI) elimination.

Image analysis method for heterogeneity and porosity characterization of biomimetic hydrogels.

This work presents an image processing procedure for characterization of porosity and heterogeneity of fully hydrated hydrogels based on the analysis of cryogenic scanning electron microscopy (cryo-SEM) images. An algorithm consisting of different filtering, morphological transformation, and thresholding steps to denoise the image whilst emphasizing the hydrogel fibres edges for extracting the pores features is explained. Finally, the information of hydrogel porosity and heterogeneity is presented in form of pore size distribution, spatial contours maps and kernel density dot plots. The obtained results reveal that a non-parametric kernel density plot effectively determines the spatial heterogeneity and porosity of the hydrogel.

Micro energy dispersive x-ray fluorescence as a powerful complementary technique for the analysis of bimetallic Au/Ag/glass nanolayer composites used in surface plasmon resonance sensors.

It is demonstrated that any theoretical analysis of experimental surface plasmon resonance (SPR) curves of metallic nano bilayers preferably should be accompanied by a more sensitive technique that is less prone to experimental errors. Micro energy dispersive x-ray fluorescence has been shown to be a powerful technique for predicting SPR angle and assessing Au/Ag nanolayer composite spatial homogeneity.

Functionalized mesoporous silicon for targeted-drug-delivery.

The present work concerns a preliminary step in the production of anticancer drug loaded porous silicon (PSi) for targeted-drug-delivery applications. A successful procedure for the covalent attachment of folic acid, polyethylene glycol (PEG) and doxorubicin to hydrophilic mesoporous silicon layers is presented. A systematic approach has been followed to obtain the optimal composition of the N,N'-dicyclohexylcarbodiimide (DCC)/N-hydroxysuccimide (NHS) in dimethylsulfoxide (DMSO) solution for the surface activation process of the undecylenic acid (UD) grafted molecules to take place with minimal undesired byproduct formation. The effect of reactant concentration and kind of solvent (aqueous or DMSO) on the attachment of folic acid to the activated PSi layer has been investigated. The covalent attachment of the doxorubicin molecules to the PSi layer functionalized with folic acid and PEG is discussed. The drug release kinetics as a function of pH has been studied. The functionalized PSi particles show a high cytotoxicity compared to the equivalent amount of free drug. Cell toxicity tests show clearly that the incorporation of folate molecules increases substantially the toxicity of the loaded PSi particles. Accordingly this new functionalized PSi may be considered a proper candidate for targeted drug delivery.

Reconciliation between experimental and Monte Carlo-based simulation of the pore size distribution in mesoporous silicon.

It is demonstrated for the first time that mesoporous PS structures obtained by the electrochemical etching of p(+)(100) oriented silicon wafers might assume the peculiarity of invariance of the first peak positions in their pore size distribution curves, albeit for current densities far from the electropolishing region and at constant electrolyte composition. A new Monte Carlo-based simulation model is presented that predicts reasonably the pore size distribution of the PS layers and the observed invariance of peak position with respect to changes in current density. The main highlight of the new model is the introduction of a 'light avalanche breakdown' process in a mathematical fashion. The model is also able to predict an absolute value of 4.23 Å for the smallest pore created experimentally. It is discussed that the latter value has an exact physical meaning: it corresponds with great accuracy to the width of a void created on the surface due to the exclusion of one Si atom.