: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Graphene is a fascinating material with unique properties, such as extreme mechanical strength, ultrahigh electrical and thermal conductivities and remarkable transparency. Further reduction in the dimensionality of graphene in the form of graphene quantum dots and graphene nanoribbons has compensated for the lack of a bandgap in the extended 2D material. These nanoscale graphenes exhibit finite bandgaps because of quantum confinement, making them attractive as next-generation semiconductors. Numerous fabrication methods for various types of graphenes have been developed, which can generally be categorized into ‘top-down’ and ‘bottom-up’ procedures. These methods afford, on different production scales, a wide range of graphene structures of different sizes, shapes and quality (defect density, edge roughness and so on). Atomically precise syntheses are indispensable for fundamental research and future technological development, but the projection of the existing methods to cost-effective bulk-scale fabrication techniques is required for upcoming industrial applications of graphenes. Numerous fabrication methods have been developed so far for the production of graphenes and nanographenes. However, how practical is the bulk production of these fascinating materials? This Perspective discusses recent advances in graphene fabrication and possibilities for translation to large-scale production.

Precision synthesis versus bulk-scale fabrication of graphenes

Photoluminescent nanosized allotropes of carbon have attracted considerable interest because of their diverse optical properties depending on their crystal structure, size, and morphology, and chemical functionalization. Here, we present the first critical review covering the photoluminescence (PL) properties, their control, and origin in various carbon allotropes and their composites. Different mechanisms by which carbon nanostructures exhibit PL are discussed, involving excitonic PL in carbon nanotubes, thermally activated delayed fluorescence in spherical fullerenes, the presence of impurity–vacancy color centers in nanodiamonds, aromatic sp2 domains in reduced graphene oxide, and surface chromophores or defect-related PL in carbon dots. We critically analyze the intrinsic and external effects affecting the PL properties (spectral shift, decay, quantum yield) from both experimental data and theoretical calculations. The key parameters addressed include, for example, the type and content of impurity ele...

Photoluminescent Carbon Nanostructures

Nitrogen-doped porous carbon is obtained by KOH activation of C60 in an ammonia atmosphere. As an anode for Li-ion batteries, it shows a reversible capacity of up to ≈1900 mA h g-1 at 100 mA g-1 . Simulations suggest that the superior Li-ion storage may be related to the curvature of the graphenes and the presence of pyrrolic/pyridinic group dopants.

Incorporating Pyrrolic and Pyridinic Nitrogen into a Porous Carbon made from C60 Molecules to Obtain Superior Energy Storage

Here, an interesting, new 0D material is presented: graphene quantum dots The new properties arising from quantum confinement and edge effects after converting 2D graphene into graphene quantum dots have attracted great interest in various disciplines, such as physics, biology, materials, and chemistry Here, the recent technological advances in the field of graphene quantum dots reported in the literature on both a theoretical and an experimental basis are highlighted Various synthesis methodologies and physical properties are discussed, along with their implementation in energy (supercapacitors, fuel cells, photovoltaic devices, light-emitting diodes), biomedical (biosensors, drug delivery, bioimaging), and environmental applications

Recent advances in graphene quantum dots: synthesis, properties, and applications

The large-scale synthesis of graphene-oxide-like quantum dots (GOLQDs) is reported by oxidizing C(60) molecules using a modified Hummers method with a yield of ≈25 wt% readily achieved. The GOLQDs are highly soluble in water and in addition to hexagons have other carbon rings in the structure. They have an average height of ≈1.2 nm and a diameter distribution of 0.6-2.2 nm after drying on substrates. First-principle calculations indicate that a possible rupturing route may include the insertion of oxygen atoms to CC bonds in the C(60) molecule, followed by rupture of that CC bonds. The GOLQD suspension has a strong photoluminescence (PL) with peak position dependent on excitation wavelength. The PL is related to the size and emissive traps caused by oxygen-containing groups. The GOLQDs also catalyze the oxidation of benzyl alcohol with a high selectivity.

Kun Ni Ni

Papers

Rupturing C60 Molecules into Graphene‐Oxide‐like Quantum Dots: Structure, Photoluminescence, and Catalytic Application