Investigation on “Excimer” Formation Mechanism of Linear Oligofluorenes‐Functionalized Anthracenes by Using Transient Absorption Spectroscopy

We study the photophysical characters of two oligofluorenes‐functionalized anthracenes molecules with different fluorine‐vinylene (FV) units, which exhibits that “excimer” state appears in the solution after photoexcitation. The dynamic data shows that two mechanisms are responsible for the generation of “excimer”. The fast one is controlled by the arene‐arene interaction between molecules and the slow one is influenced by the diffusion motion of molecules. Increasing the number of FV units may suppress the DM‐dependent “excimer” and enhance the yield of intrinsic fluorescence, which finally improves the fluorescence property of molecules in solution.     

α,β-Unsaturated acyl cyanide synthesis via triethylamine catalyzed redox cyanation

Stereoselective redox cyanation of alkynyl aldehydes was explored, furnishing (E)-α,β-unsaturated acyl cyanides. This reaction was catalyzed by mild TEA base, as a dual role of Lewis base and Brönsted base. TMSCN treated with TEA was an effective reagent for generating umpolung intermediates from alkynyl aldehydes, and this nucleophilic intermediate can be protonated by equimolar amount of EtOH, promoting the efficient conversion into α,β-unsaturated acyl cyanides. The synthesized acyl cyanides were successfully applied as the synthetic precursors in the iron-catalyzed arylation reactions.     

Modeling of the pseudo-colloids migration for multi-member decay chains with a arbitrary flux boundary condition in a fractured porous medium

A deep geologic disposal is the prime option for the long-term isolation of high-level radioactive waste (HLW) in many countries. For deeply located repositories, a radionuclide released from a failed waste container moves through the engineered and natural barriers before it reaches a biosphere. The pseudo-colloid which a radionuclide is adsorbed on a moving natural humic or fulvic colloid can be generated in a fractured porous medium. The size of a colloid is in general in the order of a hundred nanometer so that its migration velocity in a fracture is higher than that of a radionuclide due to the hydrochromatic effect. A large colloid cannot diffuse easily into a surrounding rock. Also, there are many kinds of actinides and these actinides have decay chains. In this analysis, the canonical form solution is derived for a pseudo-colloid and a solute in a fracture and a surrounding rock with a realistic inlet boundary condition with multi-member decay chains. It is used the Fortran based a computational code which uses a special subroutine for the inversion of Laplace transform. Consequently, the role of the pseudo-colloid in the fractured porous medium is important and also their decay chains aren’t neglected in the performance assessment of the HLW.     

UV irradiation gradient induced banded texture in photo-polymerized ethyl-cyanoethyl cellulose/poly(acrylic acid) cholesteric liquid crystalline films and patterns fabrication thereof

The photo-polymerization-induced banded texture of ethyl-cyanoethyl cellulose/acrylic acid/copper acrylate ((E-CE)C/AA/CuAA₂) cholesteric liquid crystalline (CLC) solutions were investigated. The results indicate that the CLC phase can be fixed by the photo-polymerization. Banded texture was obtained in the photo-polymerized CLC films. The orientation of the banded texture induced by the photo-polymerization depends on the gradient of UV irradiations on the surface of the (E-CE)C/AA/CuAA₂ CLC solutions. CLC films with different patterns can be obtained by introducing the UV irradiation gradient on the (E-CE)C/AA/CuAA₂ CLC solutions surface by using masks with different patterns. The simple approach for the fabrication of CLC films with different patterns may have the potential application in the fields of holographic image storage.     

Beating cancer in multiple ways using nanogold

Gold nanoparticles possess a unique combination of properties which allow them to act as highly multifunctional anti-cancer agents (X. H. Huang, P. K. Jain, I. H. El-Sayed and M. A. El-Sayed, Nanomedicine, 2007, 2, 681-693; P. Ghosh, G. Han, M. De, C. K. Kim and V. M. Rotello, Adv. Drug Delivery Rev., 2008, 60, 1307-1315; S. Lal, S. E. Clare and N. J. Halas, Acc. Chem. Res., 2008, 41, 1842-1851; D. A. Giljohann, D. S. Seferos, W. L. Daniel, M. D. Massich, P. C. Patel and C. A. Mirkin, Angew. Chem., Int. Ed., 2010, 49, 3280-3294). Not only can they be used as targeted contrast agents for photothermal cancer therapy, they can serve as scaffolds for increasingly potent cancer drug delivery, as transfection agents for selective gene therapy, and as intrinsic antineoplastic agents. This tutorial review will highlight some of the many forms and recent applications of these gold nanoparticle conjugates by our lab and others, as well as their rational design and physiologic interactions.     

Facile synthesis of TiO2 inverse opal electrodes for dye-sensitized solar cells

Engineering of TiO(2) electrode layers is critical to guaranteeing the photoconversion efficiency of dye-sensitized solar cells (DSSCs). Recently, a novel approach has been introduced for producing TiO(2) electrodes using the inverted structures of colloidal crystals. This paper describes a facile route to producing ordered macroporous electrodes from colloidal crystal templates for DSSCs. Using concentrated colloids dispersed in a volatile medium, the colloidal crystal templates were obtained within a few minutes, and the thickness of the template was easily controlled by changing the quantity of colloidal solution deposited. Here, the effects of the structural properties of the inverse opal TiO(2) electrodes on the photovoltaic parameters of DSSCs were investigated. The photovoltaic parameters were measured as a function of pore ordering and electrode film thickness. Moreover, DSSC applications that used either liquid or viscous polymer electrolyte solutions were investigated to reveal the effects of pore size on performance of an inverse opal TiO(2) electrode.     

Adsorption of lead(II) ions from aqueous solution on low-temperature exfoliated graphene nanosheets

Graphene nanosheets (GNSs) that were obtained by vacuum-promoted low-temperature exfoliation were used to adsorb lead ions from an aqueous system. The pristine and thermally modified GNSs were characterized with scanning electron microscopy observation and X-ray photoelectron spectroscopy analysis. It was interestingly found that the adsorption against lead ions was enhanced by heat treatment, although the oxygen complexes of GNSs showed a significant decrease. In addition, lead ion uptake resulted in an increase in the pH value of the solution. It is supposed that the Lewis basicity of GNSs is improved by heat treatment under a high vacuum, in favor of simultaneous adsorption of lead ions and protons onto GNSs.     

Strong response of multilayer polyelectrolyte films to cationic surfactants

The influence of common cationic surfactants on the physical properties of differently composed polyelectrolyte films prepared by the layer-by-layer (LbL) technology was investigated. Free-standing polyelectrolyte films as microcapsules showed a fast, strong response to the addition of less than 1 mM cationic surfactant cetyltrimethylammonium bromide (CeTAB). As a function of the polyelectrolyte composition, the behavior of the capsules varied from negligible changes to complete disintegration via strong swelling. The response of microcapsules consisting of (poly(allylamine hydrochloride)(PAH)/poly(styrene sulfonate)(PSS))(4) was associated with a 5-fold volume increase, a fast switch of permeability, and in the case of fluorescently labeled films a 4-fold increase in fluorescence intensity. The kinetics and strengths of the interaction process were investigated by confocal laser scanning microscopy (CLSM) and fluorescence spectroscopy. Also, the relative stabilities of the polycation/polyanion and surfactant/polyanion complexes were determined. A mechanism was suggested to explain the interactions between the cationic surfactants and polyelectrolyte capsules. The strong response can be exploited in potential applications such as the triggered release of drugs or other encapsulated materials, the fluorescence-based detection of cationic detergents, and a switchable stopper in microchannels. However, the high sensitivity of LbL films to traces of cationic surfactants can also limit their applicability to the encapsulation of drugs or other materials because pharmaceutical or technical formulations often contain cationic surfactants as preservatives such as benzalkonium salts (BAC). It was demonstrated that undesired capsule opening can be effectively prevented by cross-linking the polyelectrolyte multilayers.     

Biomimetic anchors for antifouling and antibacterial polymer brushes on stainless steel

Barnacle cement (BC) was beneficially applied on stainless steel (SS) to serve as the initiator anchor for surface-initiated polymerization. The amine and hydroxyl moieties of barnacle cement reacted with 2-bromoisobutyryl bromide to provide the alkyl halide initiator for the surface-initiated atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA). The hydroxyl groups of HEMA polymer (PHEMA) were then converted to carboxyl groups for coupling of chitosan (CS) to impart the SS surface with both antifouling and antibacterial properties. The surface-functionalized SS reduced bovine serum albumin adsorption, bacterial adhesion, and exhibited antibacterial efficacy against Escherichia coli (E. coli). The effectiveness of barnacle cement as an initiator anchor was compared to that of dopamine, a marine mussel inspired biomimetic anchor previously used in surface-initiated polymerization. The results indicate that the barnacle cement is a stable and effective anchor for functional surface coatings and polymer brushes.