Thermally Activated Upconversion with Metal-Free Sensitizers Enabling Exceptional Anti-Stokes Shift and Anti-counterfeiting Application.

Photochemical upconversion (UC) via triplet-triplet annihilation (TTA) has attracted considerable attention for its potential applications in solar energy conversion, photocatalysis, and bioimaging. Achieving a large anti-Stokes shift in photochemical UC is appealing but still a great challenge, especially for purely organic sensitizers. Here, we develop solid-state TTA UC systems with metal- and heavy atom-free dyes as the sensitizers, which sensitize the 9,10-diphenylanthracene acceptor through thermally activated triplet-triplet energy transfer. Solid-state UC emission with remarkable anti-Stokes shifts up to 1.10 eV is achieved owing to an evident enthalpy gain by the endothermic sensitization. The solid upconverter shows air-stable UC emission and potentials in dual-mode anti-counterfeiting and encryption applications. The present UC approach involving thermally activated sensitization enabled by purely organic dyes provides a versatile strategy to develop TTA UC materials with large anti-Stokes shift, air-tolerant emission, and environmental compatibility, which would have promising applications in information encryption, photochemical conversion, and bioimaging.

Lanthanide Supermolecular Transformers Induced by K+ and CO2.

The transfer of configuration information from supramolecular helices is a ubiquitous phenomenon in nature. DNA and proteins often change their helical structure in response to particular external stimuli and can activate important related events through sophisticated mechanisms. Attempts to create artificial multiple-stranded helicates that can adjust the configuration under external stimuli have also met with limited success. Using a simple ligand, we now show multiple-stranded lanthanide helicates that transform efficiently. Lanthanide and ligand are successfully self-assembled into different multiple helical supermolecular clusters using different templates. Additionally, these intelligent supermolecular transformers can also be transformed by different external stimuli and realize the selective recognition and fixation of the corresponding ions and molecules.

Exploring membrane domains using native membrane sheets and transmission electron microscopy.

The flow of information in cells requires the constant remodeling of cell signaling and trafficking networks. To observe the remodeling events associated with activation of receptors on the cell surface, the authors have generated and analyzed high-resolution topographical maps of colloidal gold nanoprobes (3-10 nm) marking receptors, signaling proteins, and lipids in native membranes. The technology involves sandwiching of cells between glass cover slips and electron microscopy (EM) grids, followed by ripping. Membrane sheets on EM grids are fixed, labeled with functionalized nanoprobes, and imaged by transmission electron microscopy. Probe coordinates are extracted from digitized images and the distributions of the probes are analyzed with respect to each other and to membrane features like clathrin-coated pits, caveolae, and the cortical cytoskeleton.