Organic materials with long‐lived, color‐tunable phosphorescence are potentially useful for optical recording, anti‐counterfeiting, and bioimaging. Herein, we develop a series of novel host–guest organic phosphors allowing dynamic color tuning from the cyan (502 nm) to orange red (608 nm). Guest materials are employed to tune the phosphorescent color, while the host materials interact with the guest to activate the phosphorescence emission. These organic phosphors have an ultra‐long lifetime of 0.7 s and a maximum phosphorescence efficiency of 18.2 %. Although color‐tunable inks have already been developed using visible dyes, solution‐processed security inks that are temperature dependent and display time‐resolved printed images are unprecedented. This strategy can provide a crucial step towards the next‐generation of security technologies for information handling.

Figure 2. Steroid based host matrix in realizing RTP emission. (a) Chemical structures of steroid host and second amino-substituted deuterated carbon as well as the design principle in realizing the RTP emission. Reproduced with permission. 39 Copyright 2013, Wiley. (b) Chemical structures of host 4, guest 3, and dispersant 5 as well as the application in thermal reversible recording materials. Reproduced with permission. 40 Copyright 2013, Wiley. (K r = phosphorescent decay rate, K q = rate of quenching long-lived triplet excitons).

The linear viscoelastic responses for a series of polyelectrolyte complexes, PECs, made from pairs of poly [3-(methacryloylamino)propyltrimethylammonium chloride], a polycation, and poly(sodium methacrylate), a polyanion, having various molecular weights were measured. Time−temperature superposition (TTS) for broad and narrow molecular weight distributions revealed entangled behavior at low salt concentration for the longer polyelectrolytes studied. All characteristic lifetimes were slowed by "sticky" dynamics of positive, Pol + and negative, Pol − , pairing. Time−temperature−salt doping superposition (TTSS) was achieved by considering the dual effects of increasing salt concentration on PECs: the partner lifetimes of Pol + and Pol − were inversely proportional to [NaCl], as was the population of Pol + Pol − pairs. Relaxation times for polymer partnering, entanglement, and reptation were measured directly on some systems. Whereas the intrinsic (in the absence of salt ions) lifetime for Pol + Pol − pairs was determined to be on the order of 1 × 10 −4 s, salt doping provided a faster, extrinsic, channel for relaxation at the monomer scale. The time−salt shift factor was decomposed into contributions from Pol + Pol − partner lifetimes, the number density of Pol + Pol − pairs, and the volume fraction of polymer.

A water-soluble, 'turn-on' fluorescent chemosensor based on aggregation-induced emission (AIE) has been developed. It exhibits rapid response, excellent selectivity, and sensitivity to Al(3+).