ABSTRACT
Layered semiconductors of the V-VI group have attracted considerable attention in optoelectronic applications owing to their atomically thin structures. They offer thickness-dependent optical and electronic properties, promising ultrafast response time, and high sensitivity. Compared to the bulk, 2D bismuth selenide (Bi2Se3) is recently considered a highly promising material. In this study, 2D nanosheets are synthesized by prolonged sonication in two different solvents, such as N-methyl-2-pyrrolidone (NMP) and chitosan-acetic acid solution (CS-HAc), using the liquid-phase exfoliation (LPE) method. X-ray diffraction confirms the amorphous nature of exfoliated 2D nanosheets with maximum peak intensity at the same position (015) crystal plane as that obtained in its bulk counterpart. SEM confirms the thin 2D nanosheet-like morphology. Successful exfoliation of Bi2Se3 nanosheets up to five layers is achieved using CS-HAc solvent. The as-synthesized 2D nanosheets in different solvents are employed to fabricate the photodetector. At minimum selected power density, the photodetector fabricated using exfoliated ultrathin 2D nanosheets exhibits the highest range of responsivity, varying from 15 to 2.5 mA/W, and detectivity ranging from 2.83 × 109 to 6.37 × 107. Ultrathin 2D Bi2Se3 nanosheets have fast rise and fall times, ranging from 0.01 to 0.12 and 0.01 to 0.06 s, respectively, at different wavelengths. Ultrathin Bi2Se3 nanosheets have improved photodetection parameters as compared to multilayered nanosheets due to the high surface to volume ratio, reduced recombination and trapping of charge carrier, improved carrier confinement, and faster carrier transport due to the thin layer.
ABSTRACT
Hepatic malignancies account for 1-4% of all childhood solid tumours and Hepatoblastoma is the most common malignant liver tumour in children. Its extrahepatic origin is rare. Here we present the case of a three-year-old boy who came with a large non-tender mass in the right upper abdomen for six months. Ultrasound abdomen revealed a huge heterogenous mass anterior to the right kidney and inferior to the liver with internal vascularity and calcifications, mimicking a neuroblastoma. Tru-cut needle biopsy showed foetal-type hepatoblastoma. After neoadjuvant chemotherapy, the tumour was explored. It was found to be adherent to the inferior surface of the liver with no capsular breech. Hence differentiating it from exophytic growth of hepatoblastoma. The tumour was completely resected. The postoperative course was uneventful and adjuvant chemotherapy was given. So far only a few cases of extrahepatic hepatoblastoma have been reported.
