The preparation of organic/inorganic hybrid materials composed of either small molecules or conjugated polymers and semiconductor nanoparticles (SC-NPs) has been pursued as a route to photoelectrocatalytic thin films 1 and thin films with enhanced efficiencies for photovoltaic devices. 2-5 Nanoparticle inclusions (e.g., CdSe) in hole transporting polymers create percolation pathways for electron transport. The efficiency of such hybrid solar cells depends on the morphology of the nanocrystal, the capping ligands surrounding the SC-NP, and processing conditions used to create NP/ polymer hybrid films. [2][3][4][5] The compatibility of the SC-NP with the polymer host is tailored by choice of surface capping ligand, 2c,d,4 which ultimately controls the morphologies of the two phases, and the efficiencies of charge creation and extraction from the SC-NP and polymer phases.Cadmium sulfide (CdS)-NPs have also been previously chemisorbed to electrode surfaces and their photoelectrochemical properties characterized using solution donor molecules. 1 Vectoral electron transport from the photoexcited NP occurs with high efficiency when sufficient concentrations of the electron donor are present to reduce the photo-oxidized CdS-NP, suppressing nanoparticle corrosion.We describe here a novel route to prepare nanocomposite thin films of electron-rich poly(3,4-ethylenedioxythiophene) (PEDOT) and 3,4-propylenedioxythiophene-capped CdSe nanocrystals, tethered to ITO electrodes (Scheme 1). Thin films of PEDOT were first grown on ITO electrodes, with a chemisorbed monolayer of 10- ((3-methyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-3-yl)-methoxy)-10-oxo-decanoic acid (ProDOT-CA (2)). 6 ProDOT-CA ligand-capped CdSe-NPs (3) and 2 were then cross-linked with thin PEDOT films via electropolymerization. PEDOT/3 composite films showed significantly greater photoelectrochemical activity with C 60 as the solution electron acceptor, compared to PEDOT/2 copolymer control films containing no CdSe-NPs. This approach to nanocomposite films is distinctive from previous studies of solution cast thin films of polymer/nanoparticle composites in that it enables direct wiring of the light-harvesting nanoparticle to the donor polymer and the hole collection electrode (i.e., ITO), leading toward new photoelectrocatalytic and photovoltaic technologies.ProDOT methanol (1) was prepared using reported methods 7 and converted to 2 by esterification and hydrolysis with sebacaoyl chloride. Capping ligands based on ProDOT versus EDOT were explored due to the synthetic accessibility to 1 without compromising the optoelectronic properties of the resultant polymer. 8a,11 The length of the ligand was chosen to optimize both ligand packing and NP solubility. Successive ligand exchange of hexadecylamine (HDA)-capped CdSe-NPs with pyridine, followed by ligand exchange with 2, afforded the ProDOT-CA-capped CdSe-NP (3), primarily soluble in solvents such as THF. 9 Infrared spectroscopy of the final SC-NP powders suggested nearly complete exchange of the HDA ligands ...

We demonstrate the electrochemical capture of CdSe semiconductor nanocrystals (NCs), with thiophene-terminated carboxylic acid capping ligands, at the surfaces of electrodeposited poly(thiophene) films (i) poly((diethyl)propylenedixoythiophene), P(Et)(2)ProDOT; (ii) poly(propylenedioxythiophene), PProDOT; and (iii) poly(ethylenedioxythiophene), PEDOT, coupled with the exploration of their photoelectrochemical properties. Host polymer films were created using a kinetically controlled electrodeposition protocol on activated indium-tin oxide electrodes (ITO), producing conformal films that facilitate high rates of electron transfer. ProDOT-terminated, ligand-capped CdSe-NCs were captured at the outer surface of the host polymer films using a unique pulse-potential step electrodeposition protocol, providing for nearly close-packed monolayers of the NCs at the host polymer/solution interface. These polymer-confined CdSe NCs were used as sensitizers in the photoelectrochemical reduction of methyl viologen (MV(+2)). High internal quantum efficiencies (IQEs) are estimated for photoelectrochemical sensitized MV(+2) reduction using CdSe NCs ranging from 3.1 to 7.0 nm diameters. Cathodic photocurrent at high MV(+2) concentrations are limited by the rate of hole-capture by the host polymer from photoexcited NCs. The rate of this hole-capture process is determined by (a) the onset potential for reductive dedoping of the host polymer film; (b) the concentration ratio of neutral to oxidized forms of the host polymer ([P(n)]/[P(ox)]); and (c) the NC diameter, which controls its valence band energy, E(VB). These relationships are consistent with control of photoinduced electron transfer by Marcus-like excess free energy relationships. Our electrochemical assembly methods provide an enabling route to the capture of functional NCs in conducting polymer hosts in both photoelectrochemical and photovoltaic energy conversion systems.

Chemically stabilized, porous phospholipid nanoshells (PPNs) were prepared via copolymerization of reactive monomers with unilamellar bis-Sorbyl phosphatidylcholine vesicles. The resulting PPN vesicular assemblies possess a highly porous membrane structure that allows passage of small molecules, which can react with encapsulated proteins and reporters. The unique combination of membrane stability and porosity will prove useful for preparing nm-sized sensor, container and reactor platforms stable in harsh chemical and biological environments.

G-protein-coupled receptors (GPCRs) play key roles in cellular signal transduction and many are pharmacologically important targets for drug discovery. GPCRs can be reconstituted in planar supported lipid bilayers (PSLBs) with retention of activity, which has led to development of GPCRbased biosensors and biochips. However, PSLBs composed of natural lipids lack the high stability desired for many technological applications. One strategy is to use synthetic lipid monomers that can be polymerized to form robust bilayers. A key question is how lipid polymerization affects GPCR structure and activity. Here we have investigated the photochemical activity of bovine rhodopsin (Rho), a model GPCR, reconstituted into PSLBs composed of lipids having one or two polymerizable dienoyl moieties located in different regions of the acyl chains. Plasmon waveguide resonance spectroscopy was used to compare the degree of Rho photoactivation in fluid and poly(lipid) PSLBs. The position of the dienoyl moiety was found to have a significant effect: polymerization near the glycerol backbone significantly attenuates Rho activity whereas polymerization near the acyl chain termini does not. Differences in cross-link density near the acyl chain termini also do not affect Rho activity. In unpolymerized PSLBs, an equimolar mixture of phosphatidylethanolamine and phosphatidylcholine (PC) lipids enhances activity relative to pure PC; however after polymerization, the enhancement is eliminated which is attributed to stabilization of the membrane lamellar phase. These results should provide guidance for the design of robust lipid bilayers functionalized with transmembrane proteins for use in membrane-based biochips and biosensors.

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