Mechanism and kinetics of enzymatic degradation of polyester microparticles using a shrinking particle-shrinking core model.

Generalized shrinking particle (SPM) and shrinking core (SCM) models were developed to the kinetics of heterogenous enzymatic degradation of polymer microparticles in a continuous microflow system. This enzymatic degradation was performed in a microfluidic device designed to both physically separate and immobilize the microparticles. Then time-resolved measurements were made using image processing of the physical changes of the particles during degradation.

A Robust Aqueous Core-Shell-Shell Coconut-like Nanostructure for Stimuli-Responsive Delivery of Hydrophilic Cargo.

Conventional delivery systems for hydrophilic material still face critical challenges toward practical applications, including poor retention abilities, lack of stimulus responsiveness, and low bioavailability. Here, we propose a robust encapsulation strategy for hydrophilic cargo to produce a wide class of aqueous core-shell-shell coconut-like nanostructures featuring excellent stability and multifunctionality. The numerous active groups (-SH, -NH, and -COOH) of the protein-polysaccharide wall material enable the formation of shell-cross-linked nanocapsules enclosing a liquid water droplet during acoustic cavitation.

Interfacial Dynamics within an Organic Chromophore-Based Water Oxidation Molecular Assembly.

Photoinduced electron injection, intra-assembly electron transfer, and back-electron transfer are investigated in a single-site molecular assembly formed by covalently linking a phosphonated terthiophene (T) chromophore to a Ru(terpyridine)(bipyridine)(L) (L = MeCN or HO) water oxidation catalyst adsorbed onto a mesoporous metal-oxide (MO) film. Density functional theory calculations of the T-trpy-Ru-L assembly indicate that the molecular components are strongly coupled with enhanced low-energy absorptions owing to the presence of an intraligand charge transfer (ILCT) transition between the T and trpy moieties. Ultrafast spectroscopy of the MO//T-trpy-Ru-L assemblies reveals that excitation of the surface-bound T chromophore results in ps-ns electron injection into the metal-oxide conduction band.

Role of Macromolecular Structure in the Ultrafast Energy and Electron Transfer Dynamics of a Light-Harvesting Polymer.

Ultrafast energy and electron transfer (EnT and ET, respectively) are characterized in a light-harvesting assembly based on a π-conjugated polymer (poly(fluorene)) functionalized with broadly absorbing pendant organic isoindigo (iI) chromophores using a combination of femtosecond transient absorption spectroscopy and large-scale computer simulation. Photoexcitation of the π-conjugated polymer leads to near-unity quenching of the excitation through a combination of EnT and ET to the iI pendants. The excited pendants formed by EnT rapidly relax within 30 ps, whereas recombination of the charge-separated state formed following ET occurs within 1200 ps.

Efficient Light-Driven Oxidation of Alcohols Using an Organic Chromophore-Catalyst Assembly Anchored to TiO2.

The ligand 5-PO3H2-2,2':5',2″-terthiophene-5-trpy, T3 (trpy = 2,2':6',2″-terpyridine), was prepared and studied in aqueous solutions along with its metal complex assembly [Ru(T3)(bpy)(OH2)](2+) (T3-Ru-OH2, bpy = 2,2'-bipyridine). T3 contains a phosphonic acid group for anchoring to a TiO2 photoanode under aqueous conditions, a terthiophene fragment for light absorption and electron injection into TiO2, and a terminal trpy ligand for the construction of assemblies comprising a molecular oxidation catalyst. At a TiO2 photoanode, T3 displays efficient injection at pH 4.

Decacyclene Trianhydride at Functional Interfaces: An Ideal Electron Acceptor Material for Organic Electronics.

We report the interface energetics of decacyclene trianhydride (DTA) monolayers on top of two distinct model surfaces, namely, Au(111) and Ag(111). On the latter, combined valence band photoemission and X-ray absorption measurements that access the occupied and unoccupied molecular orbitals, respectively, reveal that electron transfer from substrate to surface sets in. Density functional theory calculations confirm our experimental findings and provide an understanding not only of the photoemission and X-ray absorption spectral features of this promising organic semiconductor but also of the fingerprints associated with the interface charge transfer.

Polyimide dendrimers containing multiple electron donor-acceptor units and their unique photophysical properties.

A high-yielding synthesis of a series of polyimide dendrimers, including decacyclene- and perylene-containing dendrimer D6, in which two types of polyimide dyes are present, is reported. In these constructs, the branching unit is represented by trisphenylamine, and the solubilizing chains by N-9-heptadecanyl-substituted perylene diimides. The photophysical properties of the dendrimers have been studied by absorption, steady-state, and time-resolved emission spectroscopy and pump-probe transient absorption spectroscopy.

N-alkyldinaphthocarbazoles, azaheptacenes, for solution-processed organic field-effect transistors.

Substituted N-alkyldinaphthocarbazoles were synthesized using a key double Diels-Alder reaction. The angular nature of the dinaphthocarbazole system allows for increased stability of the conjugated system relative to linear analogues. The N-alkyldinaphthocarbazoles were characterized by UV-vis absorption and fluorescence spectroscopy as well as cyclic voltammetry.

Electron injection barrier reduction for organic light-emitting devices by quinacridone derivatives.

Water/alcohol-soluble quinacridone derivatives have been synthesized and utilized as an electron injection layer in organic light-emitting diodes. Initial results are very promising, as a device with a layer of Na(+)QHSO(3)(-) adjacent to an Al cathode exhibited a luminance efficiency (1.65 cd A(-1)) that was significantly enhanced relative to the efficiency (0.