Recently, research on QD solids has attracted interest because one cannot use the as-prepared colloidal QDs for applications requiring electrical transport properties due to the poor inter-dot charge transport mechanism. By interconnecting the QDs together, one can prepare a solid system with the desired absorption and emission properties. It is even possible to prepare an alternative material to silicon by this method. However, the preparation of such QD solid structures is a challenging process and, to the best of our knowledge, only a few reports are available on the successful preparation of QD solid systems, mostly involving inorganic systems such as PbS, CdSe and PbSe31,32,33,34. As far as such QD solid preparation is concerned, different shaped/faceted nanocrystals made up of heavier elements were interconnected with lighter organic/inorganic groups by slow evaporation and ligand exchange processes35. Such inorganic QD solid systems are weakly coupled and sensitive to external parameters such as temperature, thus limiting the effective utilization of the QD solid systems. The strong coupling between QDs is required for the effective usage of QD solid systems in a wide range of applications such as terahertz lasing and quantum computing35, 36. In the present work, we have successfully prepared GQD solid sheet structures of a single-crystalline nature by interconnecting GQDs with metal atoms. Since the basic building block (GQD) is made up of a light element and is of planar dimensions, it was possible to interconnect them through heavier metal atoms, and thus a stronger coupling is established between the GQDs. Oxygen has also played an important role in the interconnection process. The isolated sp2 domains were created in the interconnection process, which in turn helped to retain the quantum behaviour of the individual dots in the solid sheet. As a consequence, a new material system of graphene with a band gap was made possible. In this present paper, we discuss these results in detail.
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A protocol for the preparation of iron oxide nanocrystals of two different (nanorods and octahedrons) morphologies has been developed and the synthesized nanocrystals were well characterized by TEM and XRD. These two nanocrystals have been applied for the selectivie oxidation of aryl-methanol and vinyl-arene. Moreover, the magnetic catalysts have easily separated from reaction mixture by a magnet and are reused without appreciable loss of catalytic activity. The oxidation processes avoid the use of toxic catalysts and volatile and hazardous organic solvents.
In conclusion, a protocol has been developed for the preparation of iron oxide nanoparticles of two different (nanorods and octahedrons) morphologies and well characterized by TEM and XRD. These two nanomaterials showed comparable selectivity on the oxidation of aryl-methanol and vinyl-arene. Moreover, the magnetic catalysts have easily separated from reaction mixture by a magnet and are reused without appreciable loss of catalytic activity. The oxidation processes avoid use of toxic catalysts and volatile and hazardous organic solvents. Certainly, this observation provides great promise towards more practical applications. 2ff7e9595c
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