Excited state dynamics study of the self-trapped exciton formation in silicon nanosheets

After excitation to S₁ (1), the exciton takes ∼450–850 femtoseconds to relax into the self-trapped (ST) state (2) with the occurrence of strong localization and a large Stokes shift, due to the significant stretching of the Si–Si bonds.

Fullerene-doped polyaniline as new redox nanoprobe and catalyst in electrochemical aptasensor for ultrasensitive detection of Mycobacterium tuberculosis MPT64 antigen in human serum

Tuberculosis caused by Mycobacterium tuberculosis (MTB) is still a major threat to global public health. However, the existing methods for MTB detection are usually complicated and time consuming with unsatisfactory sensitivity and specificity. In this work, a relatively simple and ultrasensitive electrochemical aptasensor based on novel signal generation and amplification was constructed for the determination of MTB antigen MPT64. The coil-like fullerene (C₆₀)-doped polyaniline (C₆₀-PAn) nanohybrids with large surface area, abundant active groups and excellent electric performance were synthesized and used both as new redox nanoprobe and catalyst for the generation and amplification of electrochemical signal for the first time. Then gold nanoparticles decorated C₆₀-PAn nanocomposites (GNPs-C₆₀-PAn) were labeled with signal aptamer to form the tracer label. After the sandwich reaction of target MPT64 antigen between capture aptamer and the tracer label, a distinguishing detection signal of C₆₀-PAn would be observed. Moreover, the detection signal could be enormously enhanced towards the efficient electrocatalytic oxidation of ascorbic acid based on C₆₀-PAn, resulting in further improvement of the sensitivity. With the excellent redox and electrocatalytic activity of C₆₀-PAn, a wide detection linear range from 0.02 to 1000 pg/mL was obtained with a detection limit of 20 fg/mL for MPT64. The proposed aptasensor showed high selectivity to target antigen compared with possible interfering substances. More importantly, it also exhibited excellent specificity and sensitivity for MPT64 detection in serum samples of tuberculosis patients, which provided a rapid and efficient detection method for MTB infection.

Significantly enhanced mechanical and electrical properties of epoxy nanocomposites reinforced with low loading of polyaniline nanoparticles

Enhanced mechanical and electrical properties were observed in the polyaniline–epoxy nanocomposites prepared by three different techniques.

Magnetoresistive polyaniline–silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity

Both negative permittivity and high magnetic field resistance sensitivity are observed in silicon carbide/polyaniline nanocomposites.

Electrochemical energy storage by polyaniline nanofibers: high gravity assisted oxidative polymerization vs. rapid mixing chemical oxidative polymerization

A rotating packed bed (RPB) rather than stirred tank reactor (STR) produces more uniform polyaniline fibers with better energy storage performance.

Magnetoresistive polyaniline/multi-walled carbon nanotube nanocomposites with negative permittivity

Contrary to the observed positive giant magnetoresistance (GMR) in as-received multi-walled carbon nanotubes (MWNTs), pure polyaniline (PANI) synthesized with Cr(vi) as oxidant and MWNTs/PANI nanocomposites with ammonium persulfate (APS) as oxidant, a room temperature negative GMR of around -2% was reported in MWNTs/PANI nanocomposites with Cr(vi) as oxidant. Different from a frequency switch of permittivity from negative to positive in MWNTs/PANI nanocomposites with APS as oxidant, unique negative permittivity was observed in MWNTs/PANI nanocomposites with Cr(vi) as oxidant within the measured frequency range from 20 to 2 × 10(6) Hz. The obtained unique negative permittivity was explained by the plasma frequency from the Drude model, at which the permittivity changes from negative to positive and the material changes from a metamaterial to an ordinary dielectric medium. The observed positive and negative GMR behaviors in these disordered systems as verified by the temperature dependent resistivity exploration were well explained through a wave-function shrinkage model and orbital magnetoconductivity theory by calculating the changed localization length (a0).