Intricate Reaction Pathways on CH3NH3PbI3 Photocatalysts in Aqueous Solution Unraveled by Single-Particle Spectroscopy

Organic–inorganic hybrid perovskites such as MAPbI₃ (MA⁺ = CH₃NH₃⁺) have emerged as promising materials for solar cells and light-emitting devices. Despite their poor stability against moisture, perovskites work as hydrogen-producing photocatalysts or photosensitizers in perovskite-saturated aqueous solutions. However, the fundamental understanding of how chemical species or support materials in the solution affect the dynamics of the photogenerated charges in perovskites is still insufficient. In this study, we investigated the photoluminescence (PL) properties of MAPbI₃ nanoparticles in aqueous media at the single-particle level. A remarkable PL blinking phenomenon, along with significant decreases in the PL intensity and lifetime compared to those in ambient air, suggested temporal fluctuations in the trapping rates of photogenerated holes by chemical species (I– and H₃PO₂) in the solution. Moreover, electron transfer from the excited MAPbI₃ to Pt-modified TiO₂ proceeds in a concerted fashion for photocatalytic hydrogen evolution under the dynamic solid–solution equilibrium condition

Controllable synthesis of MoS2/graphene low-dimensional nanocomposites and their electrical properties

© 2019 Elsevier B.V.In this study, a novel hydrothermal route has been developed for the synthesis of MoS2/graphene composite with controllable structures, in which ammonium molybdatetetrahydrate, as-prepared graphene oxide (GO), and thioacetamide were used as staring materials. Effects of Mo4+-to-C precursor ratios and crystalline time on the structures, components and morphologies of MoS2/graphene were investigated. MoS2/graphene samples were characterized using XRD, FESEM, HRTEM, FTIR, Raman spectroscopy, HAADF-STEM/EDS, HXPES and electrical measurements. The results show that petal-like MoS2 nanostructures with ultrathin petals (~1–10 layers) and coexistence of 1T- and 2H-MoS2 phases can be synthesized on graphene surface in a short time (~2 h). Comparison of crystallization conditions, we found that the crystallization time had a significant effect on the size of the MoS2 nanopetals. The shorter the reaction time is, the thinner the petal-like MoS2 nanoscale is. On the other hand, by adjusting the ratios of Mo4+to C (denoted as: MoS2/C (1:2), MoS2/C (3:2), MoS2/C (2.5:1) and MoS2/C (3:1)), different MoS2/graphene architectures including “sandwich-liked”, “layer–by–layer” and “anchored” can be obtained. On the basis of these results, a possible growth mechanism of MoS2nanopetals on GO was proposed. Interestingly, the as-synthesized material depicts its memristive behavior through the Volt-Ampere characteristics, suggesting a potential application in logic memory devices11Nsciescopu

Parathyroid carcinoma: impact of preoperative diagnosis on the choice of surgical procedure

The operative procedure in the surgical treatment of parathyroid carcinoma differs from that of benign hyperparathyroidism. However, preoperative differentiation is often difficult. This study elucidated how clinicians diagnose parathyroid carcinoma and the relationship between preoperative diagnosis and the operative course. Using a retrospective chart review, twenty cases of parathyroid carcinoma from nine participating centers were examined. In 11 cases with preoperative suspicion of malignancy, at least one of these three features was found: elevated serum calcium level (>14 mg/dL), palpable mass, and irregular margin on ultrasonography. Although an intact parathyroid hormone (iPTH) threshold to suspect malignancy has not been established, six cases showed marked iPTH elevation exceeding 8.0 times the upper limit of normal. One case was excluded from analysis due to hemodialysis. Compared with the four cases that showed calcium elevation, the iPTH threshold might represent better sensitivity. Among 9 cases of benign preoperative diagnosis, six cases were performed with pericapsular resection. In three cases where malignancy was suspected in the middle of the operation, the recommended en bloc resection with ipsilateral thyroid lobectomy was not performed but a parathyroidectomy with surrounding soft tissue. In contrast, 10 preoperatively suspected cases underwent en bloc resection, and one case underwent pericapsular resection followed by supplementary ipsilateral hemithyroidectomy due to the uncertain pre- and intraoperative findings to determine the diagnosis. In conclusion, the surgical procedure for parathyroid carcinoma strongly depends on the preoperative diagnosis. The presence of excessive iPTH levels might contribute to improved preoperative diagnostic sensitivity for parathyroid carcinoma