Weak light absorption of graphene has limited the responsivity of graphene-based photodetectors. On the other hand, the slow response of PbSe as a mid-infrared range (MIR) detector makes this type of detector unsuitable as a commercial detector. Here, we report a fast MIR detector based on hybrid graphene-PbSe nanorods. For this purpose, a few-layer graphene piece was synthesized using a simple, scalable, and economical method on a cobalt layer, the synthesized graphene was transferred onto interdigitated copper electrodes, and then synthesized nanorods were spin coated on the transferred graphene. Strong and tunable light absorption in the quantum dot layer creates electric charges, which are transferred to the graphene, and due to the high charge mobility of graphene and long trapped-charge lifetimes in the quantum dot layer, they recirculate many times. The fabricated device has high speed and responsivity. The gain of fabricated detectors based on hybrid graphene quantum dots is 10.3 times more, their response time is 14.3 times faster, and their responsivity is 10 times more than conventional nanorod-based detectors. From the point of view of spectral selectivity, tuning the size of the nanorods helps optical detection from the IR to mid-IR.

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Abstract:In this paper, the synthesis of silica-coated magnetite nanoparticles using a one-step electrochemical method and their application for dye removal are presented. In this method, pure iron in a dilute aqueous sodium silicate solution that served as a silica precursor was electro-oxidized. The silica-coated magnetite nanoparticles produced by this method is nearly spherical with the size of approximately 10 nm and follows the spinel structure of Fe3O4. The silica-coated magnetite nanoparticles exhibit nearly superparamagnetic properties and excellent performance to remove methylene blue from wastewater. The adsorption capacity of the nanoparticles was approximately 24.2 mg methylene blue/g adsorbent, which was much higher than that of pure magnetite nanoparticles (1.1 mg methylene blue/g adsorbent). Also, the percentage removal was higher than 90% with the initial concentration of methylene blue up to 40 mg/L. It can be regenerated and reused with an only slight reduction in percentage removal.

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