Copolymers of Gelatin-graft-poly(3-hexylthiophene) for Transient Electronics.

As transient electronics continue to advance, the demand for new materials has given rise to the exploration of conducting polymer (CP)-based electronic materials. The big challenge lies in balancing conductivity while introducing controlled degradable properties into CP-based transient materials. In response to this, we present in this work a concept of using conducting polymers attached to an enzymatically biodegradable biopolymer to create transient polymer electronics materials. Specifically, poly(3-hexyl thiophene) (P3HT) is covalently grafted onto biopolymer gelatin, affording graft copolymer gelatin-graft-poly(3-hexyl thiophene) (termed Gel-g-P3HT). The thin films of Gel-g-P3HT that were produced by optimized processing solvent (THF/H2O cosolvent) showed enhanced π-π stacking domains of P3HT, resulting in semiconducting thin films with good electroactivity. Due to the presence of amide bonds in the gelatin backbone, Gel-g-P3HT underwent degradation over a period of 5 days, resulting in the formation of amphiphilic micellar nanoparticles that are biocompatible and nontoxic. The potential of these conductive and degradable graft copolymers was demonstrated in a pressure sensor. This research paves the way for developing biocompatible and enzymatically degradable polymer materials based on P3HT, enabling the next generation of transient polymer electronics for diverse applications, such as skin, implantable, and environmental electronics.

Toward cheaper light harvesting systems: Using earth-abundant metal oxide nanoparticles in self-assembled peptide-porphyrin nanofibers.

Cheap artificial light harvesting systems, which competently harvest solar energy and promote efficient energy transfer, are highly sought after in the renewable sector. We report the synthesis of self-assembled peptide-porphyrin fibers (SJ 6) fabricated with iron(III) oxide (Fe3 O4 ) nanoparticles as feasible electron acceptors. Charge-complementarity between the negatively charged peptide (20E) and the protonated Zn-tetraphenyl porphyrin (ZnTPyP) led to an ordered assembly of the ZnTPyP molecules, enabling efficient light harvesting. X-ray diffraction data indicates a more ordered structure in SJ 6 compared to 20E and ZnTPyP. The incorporation of Fe3 O4 nanoparticles into SJ 6 showed significant fluorescence quenching, indicating efficient electron flow from the donor to the acceptor. The SJ 6-nFe3 O4 system performed the light reaction of photosynthesis as confirmed by the reduction of 1 mM NAD+ to 0.180 mM NADH upon exposure to visible light (Xe lamp λ > 420 nm) for 1 h. The photochemical regeneration of NADH using the SJ 6-nFe3 O4 system was coupled to glutamate dehydrogenase-catalyzed conversion of α-ketoglutarate to L-glutamate. These results confirm the successful synthesis of an artificial light harvesting peptide-porphyrin system with Fe3 O4 nanoparticles as promising low-cost electron separators.

Electroactive Metal Complexes Covalently Attached to Conductive PEDOT Films: A Spectroelectrochemical Study.

The successful covalent attachment, via copper(I)-catalyzed azide alkyne cycloaddition (CuAAC), of alkyne-functionalized nickel(II) and copper(II) macrocyclic complexes onto azide (N3)-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) films on ITO-coated glass electrodes is reported. To investigate the surface attachment of the selected metal complexes, which are analogues of the cobalt-based complex previously reported to be a molecular catalyst for hydrogen evolution, first, three different PEDOT films were formed by electropolymerization of pure PEDOT or pure N3-PEDOT, and last, 1:2N3-PEDOT:PEDOT were formed by co-polymerizing a 1:4 mixture of N3-EDOT:EDOT monomers. The successful surface immobilization of the complexes on the latter two azide-functionalized films, by CuAAC, was confirmed by X-ray photoelectron spectroscopy (XPS) and electrochemistry as well as by UV-vis-NIR and resonance Raman spectroelectrochemistry. The ratio between the N3 groups, and hence, the number of surface-attached metal complexes after CuAAC functionalization, in pristine N3-PEDOT versus 1:2N3-PEDOT:PEDOT is expected to be 3:1 and seen to be 2.86:1 with a calculated surface coverage of 3.28 ± 1.04 and 1.15 ± 0.09 nmol/cm2, respectively. The conversion, to the metal complex attached films, was lower for the N3-PEDOT films (Ni 74%, Cu 76%) than for the copolymer 1:2N3-PEDOT:PEDOT films (Ni 83%, Cu 91%) due to the former being more sterically congested. The Raman and UV-vis-NIR results were simulated using density functional theory (DFT) and time-dependent DFT (TD-DFT), respectively, and showed good agreement with the experimental data. Importantly, the spectroelectrochemical behavior of both anchored metal complexes is analogous to that of the free metal complexes in solution. This proves that PEDOT films are promising conducting scaffolds for the covalent immobilization of metal complexes, as the existing electrochromic features of the complexes are preserved on immobilization, which is important for applications in electrocatalytic proton and carbon dioxide reduction, optoelectronics, and sensing.

Molecular "Building Block" and "Side Chain Engineering": Approach to Synthesis of Multifunctional and Soluble Poly(pyrrole phenylene)s.

Here, the synthesis of a novel poly(pyrrole phenylene) (PpyP) that is both modular in ways of functionalization and soluble in organic solvents is reported, and therefore solution processable. This is achieved through the functionalization of the side-chain substituents in pyrrole phenylene (PyP) repeating units. t Butyl acrylate brushes are first grafted through atom transfer radical polymerization from one type of PyP, followed by oxidative chemical co-polymerization of the grafted PyP with a PyP bearing different side chains-either an azide or a methoxy moiety, resulting in a soluble PpyP where solubility is not dopant-dependent. Successful post-polymerization modification through "click" chemistry and post-polymerization processing via electrospinning are also demonstrated. Additionally, performed computational calculations indicate planarity of the novel polyrrole phenylene monomers and ionisation potentials that favor α-α bond formation during their polymerization.

Electrospun Polythiophene Phenylenes for Tissue Engineering.

This research focuses on the design of biocompatible materials/scaffold suitable for use for tissue engineering. Porous fiber mats were produced through electrospinning of polythiophene phenylene (PThP) conducting polymers blended with poly(lactide- co-glycolic acid) (PLGA). A peptide containing an arginylglycylaspartic acid (RGD) fragment was synthesized using solid phase peptide synthesis and subsequently grafted onto a PThP polymer using azide-alkyne "click" chemistry. The obtained RGD functionalized PThP was also electrospun into a fiber mat. The electrospun mats' morphology, roughness and stiffness were studied by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM) and their electroactivity by cyclic voltammetry. The fibers show excellent cytocompatibility in culture assays with human dermal fibroblasts-adult (HDFa) and human epidermal melanocytes-adult (HEMa) cells. The electrospun fibers' roughness and stiffness changed after exposing the fiber mats to the cell culture medium (measured in dry state), but these changes did not affect the cell proliferation. The cytocompatibility of our porous scaffolds was established for their applicability as cell culture scaffolds by means of investigating mitochondrial activity of HDFa and HEMa cells on the scaffolds. The results revealed that the RGD moieties containing PThP scaffolds hold a promise in biomedical applications, including skin tissue engineering.

Conducting electrospun fibres with polyanionic grafts as highly selective, label-free, electrochemical biosensor with a low detection limit for non-Hodgkin lymphoma gene.

A highly selective, label-free sensor for the non-Hodgkin lymphoma gene, with an aM detection limit, utilizing electrochemical impedance spectroscopy (EIS) is presented. The sensor consists of a conducting electrospun fibre mat, surface-grafted with poly(acrylic acid) (PAA) brushes and a conducting polymer sensing element with covalently attached oligonucleotide probes. The sensor was fabricated from electrospun NBR rubber, embedded with poly(3,4-ethylenedioxythiophene) (PEDOT), followed by grafting poly(acrylic acid) brushes and then electrochemically polymerizing a conducting polymer monomer with ssDNA probe sequence pre-attached. The resulting non-Hodgkin lymphoma gene sensor showed a detection limit of 1aM (1 × 10-18mol/L), more than 400 folds lower compared to a thin-film analogue. The sensor presented extraordinary selectivity, with only 1%, 2.7% and 4.6% of the signal recorded for the fully non-complimentary, T-A and G-C base mismatch oligonucleotide sequences, respectively. We suggest that such greatly enhanced selectivity is due to the presence of negatively charged carboxylic acid moieties from PAA grafts that electrostatically repel the non-complementary and mismatch DNA sequences, overcoming the non-specific binding.