Volume 6 Issue 7, July 2014

In this review, we discuss diffusion-driven currents in several types of organic-semiconductor diodes, including light-emitting diodes, solar cells and single-carrier devices. It is demonstrated that the ideality factor of the current and photon emission contains important information about charge transport and recombination in such devices. Most importantly, the effects of charge trapping and trap-assisted recombination can be explored. An analytical model is derived for diffusion-driven currents, which can explain the current–voltage behavior of organic diodes and allows determination of the injection barriers and built-in voltages.

In this review, the significant advances of the new type of graphene fibers (GFs) achieved during the recent few years have been systematically summarized, including the tunable and controllable preparation of GFs with functionalizations and their remarkable applications for unconventional devices such as flexible fiber-type of actuators, robots, motors, photovoltaic cells and supercapacitors.

The scope and limitations of using supramolecular interactions to control and direct energy transfer processes in self-assembled materials are discussed with emphasis on recent developments in the field.

ATP can act an ideal boosting agent for markedly improving the peroxidase-like catalytic activity over a broad temperature range.

By fabricating a pH-responsive smart device with tunable surface-wetting properties, we have realized continuous in situ separations of oil/water/oil ternary mixtures without ex situ treatments of cleaning or drying. In air, the superhydrophobic/superoleophilic surface of the smart device allowed heavy oil to permeate through while preventing water from passing. When exposed to alkaline water, the superhydrophilicity/underwater superoleophobicity of the smart device surface prevented the passage of hexane while allowing water to penetrate. In this way, efficient separation and collection of the individual components of a complex oil/water/oil mixture was realized in a continuous process with no ex situ treatments. This method could provide a strategy for continuous separations of oil/water/oil ternary mixtures, which are common in practical oil spill cases.

Four oligonucleotide strands are hybridized to form the 3D DNA nano-pyramid. Three thiol groups-terminated vertex can immobilize the pyramid firmly onto the surface of gold electrode, while the remaining non-thiolated vertex at the top with carboxyl group allows the covalent binding of anti-IgG antibody. Through traditional sandwich immunoreaction, the electroactive tag, ferrocene (FeC) generates electrochemical signals used to detect the analyte IgG. The pyramidal structure with higher rigidity encourages more uniform surface assembly and less steric effect, resulting in lower background interference. The pyramid's hollow structure further contributes to efficient electron transfer and makes this immunoassay system achieve an ultrasensitive detection limit.

3D-networked boron-doped diamond/carbon nanotube (BDD–CNT) core-shell nanowires were fabricated using the electrostatic self-assembly of nanodiamond. Although CNTs are easily etched out at their defect sites in hydrogen-rich environments, densely attached nanodiamond particles suppressed the etching of the CNTs and promoted BDD growth. After BDD deposition, 3D-networked BDD–CNT nanowires were successfully developed. In comparison to other electrodes, the BDD–CNT electrode exhibited better electrochemical performances, that is, low electron transfer resistance, large effective surface area and high sensitivity with significantly low detection range (8.7 mA mM⁻¹ in the range 0.65–83.75 nM). The improvement in the performances of the BDD–CNT electrode could be attributed to the geometry and electron pathways offered by CNTs as well as to the synergistic material properties of BDD and CNT. The BDD–CNT electrode shows promise for application in the noninvasive measurement of glucose in living beings as well as for environmental monitoring in sea water.