As opposed to inorganic counterparts, organic quantum dots often exhibit lower fluorescence efficiencies and are complex to synthesize. Here we develop nitrogen‐doped (N‐GQDs) and nitrogen–sulfur codoped (NS‐GQDs) graphene quantum dots exhibiting high‐yield visible and near‐IR emission that are synthesized via a single‐step microwave‐assisted hydrothermal technique with a single glucosamine‐HCl starting material (thiourea precursor used for NS‐GQDs). As‐synthesized N‐GQDs and NS‐GQDs are well‐dispersed (average sizes of 5.50 and 3.90 nm) with high crystallinity and pronounced G‐band. Formed by the bottom‐up assembly of glucosamine, they contain amine linkage and a variety of oxygen‐containing functional groups assessed by Fourier‐transform infrared spectroscopy with ≈2% sulfur for NS‐GQDs. The synthetic procedure allows varying their size and the bandgap. Unlike other graphene‐based quantum dots, these GQDs exhibit bright, stable fluorescence both in the visible and near‐IR with high quantum yields of up to 60%. Excitation‐dependent visible fluorescence is attributed to size‐dependent bandgaps, with near‐IR emission potentially arising from the emissive defect states/their arrangements. Advantageous properties of these GQDs are utilized to develop exciton recombination layer for organic light‐emitting devices exhibiting both photoluminescence and electroluminescence in the visible. Produced by ecofriendly one‐step scalable synthesis brightly‐emissive N‐GQDs and NS‐GQDs become a promising material for novel organic optoelectronics.

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Reactions of [Al(NMe2)3]2 with NH3, mimicking the case of the related Ga-derivative, provided an Al−amide−imide precursor that was pyrolyzed to pure nanocrystalline AlN. Based on that chemistry, a mixed Al/Ga precursor system was designed to lead to the bimetallic nitride composites. A prototype study included equilibration in hexane or toluene of the dimers [M(NMe2)3]2, M = Al, Ga, which resulted in the formation of the homoleptic four-membered-ring compound (Me2N)2Al(μ-NMe2)2Ga(NMe2)2. Crystalline [M(NMe2)3]2, M = Al/Ga (1/1), obtained from this equilibration was structurally characterized. Transamination/deamination reactions carried out with liquid NH3 in the preequilibrated bimetallic system [Al(NMe2)3]2/[Ga(NMe2)3]2, Al/Ga = 1/1, resulted in the mixed M−amide−imide precursors that were converted at 700−1100 °C to aluminum/gallium nitride nanocomposite materials. The nature of these bulk nanocomposites has been elucidated by XRD, TEM/EDS, IR, and PL techniques.

Near-infrared (NIR) emissive nanomaterials are desired for bioimaging and drug delivery applications due to the high tissue penetration depth of NIR light, enabling in vitro/ex vivo/in vivo fluorescence tracking. Considering the scarcity of NIR-fluorescing biocompatible nanostructures, we have for the first-time synthesized nanometer-sized reduced graphene oxide-derived graphene quantum dots (RGQDs) with NIR (950 nm) emission highly biocompatible in vitro with no preliminary toxic response in vivo. RGQDs are obtained in a high-yield (∼90%) top-down sodium hypochlorite/ultraviolet-driven synthetic process from non-emissive micron-sized reduced graphene oxide (RGO) flakes. This oxidation of RGO yields quantum dots with an average size of 3.54 ± 0.05 nm and a highly crystalline graphitic lattice structure with distinguishable lattice fringes. RGQDs exhibit excitation-independent emission in the visible and NIR-I region with a maximum NIR quantum yield of ∼7%. Unlike their parent material, RGQDs show substantial biocompatibility with ∼75%–80% cell viability up to high (1 mg ml−1) concentrations verified via both MTT and luminescence-based cytotoxicity assays. Tracked in vitro via their NIR fluorescence, RGQDs exhibit efficient internalization in HeLa cells maximized at 12 h with further anticipated excretion. In vivo, RGQDs introduced intravenously to NCr nude mice allow for fluorescence imaging in live sedated animals without the need in sacrificing those at imaging time points. Their distribution in spleen, kidneys, liver, and intestine assessed from NIR fluorescence in live mice, is further confirmed by excised organ analysis and microscopy of organ tissue slices. This outlines the potential of novel RGQDs as NIR imaging probes suitable for tracking therapeutic delivery in live animal models. A combination of smaller size, water-solubility, bright NIR emission, simple/scalable synthesis, and high biocompatibility gives RGQDs a critical advantage over a number of existing nanomaterials-based imaging platforms.

Two precursor routes culminating in bulk nanocrystalline gallium nitride materials are reported, with emphasis on the materials' XRD/crystalline features and photoluminescence (PL). First, the new polymeric gallium imide, {Ga(NH)3/2}n, can be converted to nanocrystalline, cubic/hexagonal GaN ranging in color from yellow to light gray. Second, a new route to gallazane, [H2GaNH2]x, from the combination of LiGaH4 and NH4X (X = Cl, Br) in Et2O is shown to result in a material that slowly converts to a polymeric solid via H2 and NH3 elimination-condensation pathways. Both the gallazane and the polymeric solid are pyrolyzed to dark gray nanocrystalline, phase-inhomogeneous GaN as above. Specific variations in the pyrolysis conditions enable some control over the particle nanosize and a degree of crystalline phase-inhomogeneity of the materials. These nanophase GaN materials have also been characterized by room temperature photoluminescence (PL) measurements. In general, the observed emission spectra are strongly dependent on pyrolysis temperature and typically exhibit weak defect yellow-green emission. While the as-prepared GaN does not exhibit band-edge PL, a brief hydrofluoric acid etch yields nanophase GaN exhibiting an intense blue-emitting PL spectrum with an emission maximum near 420 nm.