Charge-Transfer Emission of Mixed Organic Cocrystal Microtubes over the Whole Composition Range

A series of crystalline mixed cocrystal microtubes comprising organic charge-transfer (CT) complexes has been prepared. The emission colors of the mixed cocrystal microtubes can be tailored from green to orange at low dopant concentrations (0 < <i>x</i> ⩽ 5%), while their hexagonal cross sections can transform into square ones gradually at higher concentrations (0.15 < <i>x</i> < 1). In addition, we can further extend the solvent-processed synthetic route to other CT pairs based on structural compatibility consideration

Theoretical Study of the Gaseous Hydrolysis of NO₂ in the Presence of Amines

The effects on the hydrolysis of NO₂ in the presence of methylamine and dimethylamine molecules were investigated by theoretical calculations of a series of the molecular clusters 2NO₂-<i>m</i>H₂O–CH₃NH₂ (<i>m</i> = 1–3) and 2NO₂-<i>m</i>H₂O-(CH₃)₂NH (<i>m</i> = 1, 2). With methylamine included in the clusters, the energy barrier is reduced by 3.2 kcal/mol from that with ammonia, and the corresponding products may form without an energy barrier. The results show that amines have larger effects than ammonia in promoting the hydrolysis of NO₂ on thermodynamics. The additional water molecules can stabilize the transition states and the product complexes, and we infer that adding more water molecules in the reactions mainly act as solvent and promoting to form the methylamine nitrate (CH₃NH₃⁺NO₃^–). In addition, the interactions of CH₃NH₂ and (CH₃)₂NH on the hydration of HNO₃ are also more effective than NH₃, and the NH₄NO₃, CH₃NH₃NO₃, and (CH₃)₂NH₂NO₃ complexes tend to form the larger aerosols with the increasing of water molecules. The equilibrium geometries, harmonic vibrational frequencies, and intensities of both HONO–CH₃NH₂ and HONO–NH₃ complexes were investigated. Calculations predict that the binding energies of both HONO–CH₃NH₂ complexes are larger than HONO–NH₃ complexes, and the OH stretching vibrational frequencies and intensities are most affected. The natural bond orbital analysis was performed to describe the donor–acceptor interactions on a series of complexes in the reactions 2NO₂ + H₂O + CH₃NH₂ and 2NO₂ + H₂O + (CH₃)₂NH, as well as the complexes of HONO–NH₃ and HONO–CH₃NH₂. The results show that the interactions with amines are relatively larger, and the higher stabilization energies between CH₃NH₂ and HONO are found

Transfer-Free Synthesis of Doped and Patterned Graphene Films

High-quality and wafer-scale graphene on insulating gate dielectrics is a prerequisite for graphene electronic applications. For such applications, graphene is typically synthesized and then transferred to a desirable substrate for subsequent device processing. Direct production of graphene on substrates without transfer is highly desirable for simplified device processing. However, graphene synthesis directly on substrates suitable for device applications, though highly demanded, remains unattainable and challenging. Here, we report a simple, transfer-free method capable of synthesizing graphene directly on dielectric substrates at temperatures as low as 600 °C using polycyclic aromatic hydrocarbons as the carbon source. Significantly, N-doping and patterning of graphene can be readily and concurrently achieved by this growth method. Remarkably, the graphene films directly grown on glass attained a small sheet resistance of 550 Ω/sq and a high transmittance of 91.2%. Organic light-emitting diodes (OLEDs) fabricated on N-doped graphene on glass achieved a current density of 4.0 mA/cm² at 8 V compared to 2.6 mA/cm² for OLEDs similarly fabricated on indium tin oxide (ITO)-coated glass, demonstrating that the graphene thus prepared may have potential to serve as a transparent electrode to replace ITO