Tunable metallic-like transport in polypyrrole

Conjugated polymers(CPs),organic macromolecules with a linear backbone of alternating C–C and C=C bonds,possess unique semiconductive properties,providing new opportunities for organic electronics,photonics,information,and energy devices.Seeking the metallic or metallic-like,even superconducting properties beyond semiconductivity in CPs is always one of the ultimate goals in polymer science and condensed matter.Only two metallic and semi-metallic transport cases—aniline-derived polyaniline and thiophene-derived poly(3,4-ethylenedioxythiophene)—have been reported since the development of CPs for four decades.Controllable synthesis is a key challenge in discovering more cases.Here we report the metallic-like transport behavior of another CP,polypyrrole(PPy).We observe that the transport behavior of PPy changes from semiconductor to insulator-metal transition,and gradually realizes metallic-like performance when the crystalline degree increases.Using a generalized Einstein relation model,we rationalized the mechanism behind the observation.The metallic-like transport in PPy demonstrates electron strong correlation and phonon–electron interaction in soft condensation matter,and may find practical applications of CPs in electrics and spintronics.

Host-mediated biofilm forming promotes post-graphene pathogen expansion via graphene micron-sheet

Graphene is a potential candidate for applications in biomedical field.It is inevitable that graphene is in contact with the ubiquitous bacterial environment.More attention has been paid to the antimicrobial activity of graphene derivatives(graphene oxide,reduced graphene oxide)than the interaction between graphene and bacteria.Herein,we explore interaction between graphene micron-sheet and bacteria from micro(gene expression)and macro(colonies)perspectives.Results demonstrate that graphene micron-sheet accelerates the biofilm forming thus promoting pathogen expansion toward both Gram-negative bacteria E.coli and Gram-positive bacteria S.aureus.The graphene micron-sheet acts as a“habitat”for increasing bacterial attachment and biofilm forming.For E.coli,graphene micron-sheet,firstly changes the integrity of periplasmic and outer membrane components,then makes membraneassociated and cell division genes increased,and finally promotes bacterial proliferation;For S.aureus,graphene micron-sheet can accelerate biofilm forming and develop bacterial expansion owing to the regulation of the quorum-sensing system and global regulatory proteins.The work can shed new light on the range of possible mode of actions,developing a better understanding of the capabilities of graphene micronstructures.