Polyaniline was covalently grafted on pristine few-layer graphene via a perfluorophenyl azide-mediated coupling chemistry.

Native coenzymes such as the reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavin adenine dinucleotide play pivotal roles in energy metabolism and a myriad of biochemical reactions in living cells/tissues. These coenzymes are naturally fluorescent and, therefore, have the potential to serve as intrinsic biomarkers for mitochondrial activities, programmed cell death (apoptosis), oxidative stress, aging, and neurodegenerative disease. In this contribution, we employ two-photon fluorescence lifetime imaging microscopy (FLIM) and time-resolved anisotropy imaging of intracellular NADH for quantitative, non-invasive biochemistry on living cells in response to hydrogenperoxide-induced oxidative stress. In contrast with steady-state one-photon, UV-excited autofluorescence, two-photon FLIM is sensitive to both molecular conformation and stimuli-induced changes in the local environment in living cells with minimum photodamage and inherently enhanced spatial resolution. On the other hand, time-resolved, two-photon anisotropy imaging of cellular autofluorescence allows for quantitative assessment of binding state and environmental restrictions on the tumbling mobility of intrinsic NADH. Our measurements reveal that free and enzyme-bound NADH exist at equilibrium, with a dominant autofluorescence contribution of the bound fraction in living cells. Parallel studies on NADH-enzyme binding in controlled environments serve as a point of reference in analyzing autofluorescence in living cells. These autofluorescence-based approaches complement the conventional analytical biochemistry methods that require the destruction of cells/tissues, while serving as an important step towards establishing intracellular NADH as a natural biomarker for monitoring changes in energy metabolism and redox state of living cells in response to environmental hazards.

This Article reports methods to deposit iridium oxide nanoparticles (IrO x NPs) onto flexible materials for charge storage and the stable charge−discharge mechanism. In this work, IrO x NPs were electrodeposited onto commercially available flexible surfaces of both knit and nonwoven cotton and nonwoven carbon-based (carbon nanotubes and graphene) textile substrates. Carbon-coated cotton materials were fabricated by reducing graphene oxide on fabric. Flexible electrode materials were fabricated by either reducing graphene oxide on cotton fabric or binding carbon nanotubes/graphene into a free-standing platform. The IrO x NPs were then electrodeposited onto flexible platform samples by applying a positive potential to the fabric. After deposition, the resultant specific capacitance of the materials increased within the range from 192% to 2747% and was stable for over 1000 charge and discharge cycles.

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