Search

The interface between molecules and electrodes has great impact on charge transport of molecular devices. Precisely manipulating the structure and electronic coupling of electrode-molecule interface at a molecular level is very challenging. Here, we develop new molecular junctions based on tetrathiafulvalene (TTF)-fused naphthalene diimide (NDI) molecules which are anchored to gold electrodes through direct TTF-Au contacts formed via Au-S bonding. These contacts enable highly efficient orbital hybridization of gold electrodes and the conducting π-channels, yielding strong electrode-molecule coupling and remarkably high conductivity in the junctions. By further introducing additional thiohexyl (SHe) anchors to the TTF units, we develop molecular wires with multiple binding sites and demonstrate reversibly switchable electrode-molecule contacts and junction conductance through mechanical control. These findings show a superb electrode-molecule interface and provide a new strategy for precisely tunning the conductance of molecular devices towards new functions.

Imaging-guided photodynamic therapy (PDT) has been regarded as a promising strategy for precise cancer treatment. Because of their excellent modifiability and drug-loading capacity, nanoparticles have played an important role in PDT. Nonetheless, when traditional photosensitizers are made into nanoparticles, both their fluorescence and reactive oxygen species generation efficacy decrease due to a phenomenon known as aggregation-caused quenching. Fortunately, in recent years, several kinds of organic dyes with “abnormal” properties (termed aggregation-induced emission, AIE) were developed. With enhanced fluorescence emission in the nanoaggregation state, the traditional obstacles mentioned above may be overcome by AIE luminogens. Herein, we provide a better combination of photosensitizers and nanoparticles, namely, dual-function AIE nanoparticles capable of producing reactive oxygen species, to implement targeted and imaging-guided in vivo PDT. Good contrast of in vivo imaging and obvious therapeutic efficacy were observed at a low dose of AIE nanoparticles and low irradiance of light, thus resulting in negligible side effects. Our work shows that AIE nanoparticles may play a promising role in imaging-guided clinical PDT for cancer in the near future.

Hydrogen sulfide (H2S) has been found to be the third most important endogenous gaseous signaling molecule after nitric oxide (NO) and carbonic oxide (CO) and plays crucial roles in living organisms and biological systems. Here we use aggregation- induced emission (AIE) of a small organic molecule (TPE-indo) to detect H2S in both solution and living cells. TPE-indo can target mitochondria and aggregate to fluoresce, which can serve as a sensor for monitoring H2S in the mitochondria. We regulate the fluorescence of AIE molecules by tuning the viscosity of the solution to form TPE-indo nanoparticles, constructing a probe for H2S with good selectivity and high sensitivity. The nucleophilic addition of HS- to the TPE-indo is crucial for the rapid H2S detection. The imaging and analysis of H2S in mitochondria of living cells with the probe demonstrate potential biological applications.

The broad class of explosives includes nitro aromatics as well as challenging aliphatic nitro-organics whose detection is important from counter-terrorism and national security perspectives. Here we report a turn-on fluorescent sensor array based on aggregation-induced emission (AIE) fluorophores as receptors. To achieve a good sensing system with fast response, good sensitivity and low detection limit, three receptors with abundant chemical diversities for target analytes were synthesized. The turn-on response of the individual receptor showed highly variable and cross-reactive analyte-dependent changes in fluorescence. The excellent ability to identify a variety of explosives, especially the challenging aliphatic nitro-organics (2,3-dimethyl-2,3-dinitrobutane (DMNB), 1,3,5-trinitro-1,3,5-triazinane (RDX), cyclotetramethylene tetranitramine (HMX) and entaerythritol tetranitrate (PETN)), was demonstrated in qualitative and quantitative analyses with 100% accuracy. The fluorescence signal amplification in the presence of explosives allows for application of these receptors in a sensor microarray suitable for high-throughput screening. These results suggested that the cross-reactive sensor array based on AIE fluorophores could find a wide range of applications for sensing various analytes or complex mixtures.

The colorimetric response of amine-terminated polydiacetylene (PDA) vesicles was initially demonstrated by varying the pH of the solution. Convenient colorimetric methods to detect glucose and acetylcholinesterase (AChE) activity were successfully established using amine-terminated PDA vesicles by taking advantage of the following features: (1) the amine-terminated PDA vesicles undergo a colorimetric transition as the pH of the solution changes; (2) glucose can be oxidized to gluconic acid in the presence of glucose oxidase; and (3) AChE catalyzes the hydrolysis of acetylcholine to acetic acid. The visual detection of glucose levels and AChE activity showed good selectivity and acceptable sensitivity. The detection limit of glucose was ∼2.5 μmol/L and the level of AChE activity was assayed as low as 10.0 mU/mL. Moreover, the amine-terminated PDA vesicles can be used for screening the activity of inhibitors against AChE.

Tetrathiafulvalene (TTF) and its derivatives have been intensively investigated for conducting materials for more than 30 years. As π-electron donors, TTF and its derivatives can be reversibly transformed into the respective TTF·+ and TTF2+. Due to its reversible feature, the TTF unit has been widely employed as the building block for switchable systems. In recent years studies of conducting nanostructures of TTF derivatives have received more and more attention. One simple way to prepare nanostructures is through the gelation processes. In this review, we have discussed recent progress in stimuli-responsive gels and conducting nanostructures based on TTF-based gelators.

2-(4-Pyridyl)imino nitroxide and tetraphenylporphyrin zinc(II) formed a stable complex by noncovalent bonding in a nonpolar solution. Nicotine displaced 2-(4-pyridyl)imino nitroxide when it was added to a solution of 2-(4-pyridyl)imino nitroxide-tetraphenylporphyrin zinc(II). The fluorescence intensity of tetraphenylporphyrin zinc(II) was altered by sequentially addition of 2-(4-pyridyl)imino nitroxide and nicotine. This was used to develop a new method for detection of nicotine.