Owing to their narrow bright emission band, broad size-tunable emission wavelength, superior photostability, and excellent flexible-substrate compatibility, light-emitting diodes based on quantum dots (QD-LEDs) are currently under intensive research and development for multiple consumer applications including flat-panel displays and flat lighting. However, their commercialization is still precluded by the slow development to date of efficient QD-LEDs as even the highest reported efficiency of 2.0% cannot favorably compete with their organic counterparts. Here, we report QD-LEDs with a record high efficiency (approximately 4%), high brightness (approximately 6580 cd/m(2)), low turn-on voltage (approximately 2.6 V), and significantly improved color purity by simply using deoxyribonucleic acid (DNA) complexed with cetyltrimetylammonium (CTMA) (DNA-CTMA) as a combined hole transporting and electron-blocking layer (HTL/EBL). This, together with controlled thermal decomposition of ligand molecules from the QD shell, represents a novel combined, but simple and very effective, approach toward the development of highly efficient QD-LEDs with a high color purity.

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Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formation of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature.

Carbon nanopearls have a unique layered structure made of nano-sized graphene fragments, which distinguishes them from closed-shell nano-carbons. This unique structure offers beneficial tribological properties which were evaluated in humid and dry environments. The lubricating effect was related to an easy shear of nano-sized graphene flakes from individual nanopearls.

The structure and physical properties of doped fullerene materials were investigated for their interesting thermal properties. The synthesis and thermal properties of ZnxC60 thin films are reported. Thin films of ZnxC60 were found to have an exceedingly low thermal conductivity of 0.13 Wm−1 K−1. Differential scanning calorimetry results suggested that a temperature of 357 °C is needed in order to fully intercalate the Zn with the C60. Both charge transfer and covalent bonding (between Zn and C60) should be considered when attempting to understand the Raman spectra observed. Moreover, the ZnxC60 thin films created represent an interesting class of materials that could find use in several thermal applications. Furthermore, in the present case, the exceptionally low thermal conductivity is accompanied by a substantial increase in the electrical conductivity, suggesting interesting thermal and electrical transport.

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