Seeing the Unseen: The Structural Influence of the Lone Pair Electrons in PbWO4.

Pair distribution function (PDF) analysis of the scheelite-type material PbWO4 reveals previously unidentified short-range structural distortions in the PbO8 polyhedra and WO4 tetrahedra not observed in the similarly structured CaWO4. These local distortions are a result of the structural influence of the Pb2+ 6s2 lone pair electrons. These are not evident from the Rietveld analysis of synchrotron X-ray or neutron powder diffraction data, nor do they strongly influence the X-ray PDF (XPDF). This illustrates the importance of neutron PDF (NPDF) in the study of such materials. First-principles density function theory (DFT) calculations show that the Pb2+ 6s2 electrons are hybridized with the O2- 2p electrons near the Fermi level. The presence of local-scale distortions has previously been neglected in studies of structure-functionality relationships in PbWO4 and other scheelite-structured photocatalytic materials, including BiVO4, and this observation opens new avenues for their optimization.

Bamboo leaf-based carbon dots for efficient tumor imaging and therapy.

In this study, carbon dots synthesized from bamboo leaf cellulose were used simultaneously as a staining agent and for doxorubicin delivery to target cancer cells. Owing to their nontoxic properties, the production of carbon dots from bamboo leaves is a green approach involving optimized application of bamboo tree waste. For multifunctional applications, the carbon dots were modified with 4-carboxybenzylboronic acid and doxorubicin to improve target specificity and drug delivery to HeLa tumor cells. The resulting modified carbon dots were characterized using different analytical techniques, which showed that they were biocompatible, nontoxic, and highly stable over a wide range of pH values and at high ionic strengths. Furthermore, in vitro confocal microscopy studies demonstrated their blue fluorescence and cellular pathway for entering HeLa cells via folate receptor-mediated endocytosis. Cell viability data and flow cytometry results also confirmed the selective uptake of the carbon dots by HeLa cells, which significantly enhanced cell cytotoxicity.