Organic luminogens with persistent room temperature phosphorescence (RTP) have attracted great attention for their wide applications in optoelectronic devices and bioimaging. However, these materials are still very scarce, partially due to the unclear mechanism and lack of designing guidelines. Herein we develop seven 10-phenyl-10H-phenothiazine-5,5-dioxide-based derivatives, reveal their different RTP properties and underlying mechanism, and exploit their potential imaging applications. Coupled with the preliminary theoretical calculations, it is found that strong π–π interactions in solid state can promote the persistent RTP. Particularly, CS-CF3 shows the unique photo-induced phosphorescence in response to the changes in molecular packing, further confirming the key influence of the molecular packing on the RTP property. Furthermore, CS-F with its long RTP lifetime could be utilized for real-time excitation-free phosphorescent imaging in living mice. Thus, our study paves the way for the development of persistent RTP materials, in both the practical applications and the inherent mechanism.

A time-resolved Laue X-ray diffraction technique has been used to explore protein relaxation and ligand migration at room temperature following photolysis of a single crystal of carbon monoxymyoglobin. The CO ligand is photodissociated by a 7.5 ns laser pulse, and the subsequent structural changes are probed by 150 ps or 1 micros X-ray pulses at 14 laser/X-ray delay times, ranging from 1 ns to 1.9 ms. Very fast heme and protein relaxation involving the E and F helices is evident from the data at a 1 ns time delay. The photodissociated CO molecules are detected at two locations: at a distal pocket docking site and at the Xe 1 binding site in the proximal pocket. The population by CO of the primary, distal site peaks at a 1 ns time delay and decays to half the peak value in 70 ns. The secondary, proximal docking site reaches its highest occupancy of 20% at approximately 100 ns and has a half-life of approximately 10 micros. At approximately 100 ns, all CO molecules are accounted for within the protein: in one of these two docking sites or bound to the heme. Thereafter, the CO molecules migrate to the solvent from which they rebind to deoxymyoglobin in a bimolecular process with a second-order rate coefficient of 4.5 x 10(5) M(-1) s(-1). Our results also demonstrate that structural changes as small as 0.2 A and populations of CO docking sites of 10% can be detected by time-resolved X-ray diffraction.

We report the first example of an AIEgen (DPP-BO) with fluorescence-phosphorescence dual emission under mechanical stimulation. By carefully analyzing the crystal structure of DPP-BO, the efficient intermolecular and intramolecular interactions should account for its unique mechanoluminescence (ML) properties, especially the abnormal phosphorescence, as further confirmed by controlled experiments and theoretical calculations for the presence of ISC transitions. These results provide important information for understanding the complex ML process, possibly opening up a new way to study the inherent mechanism of ML by broadening the application of AIEgens.

Measurements of the in-plane magnetic field penetration depth λ ab in Fe-based superconductors with the nominal composition SmFeAsO0.85 (Tc ≃ 52 K) and NdFeAsO0.85 (Tc ≃ 51 K) were carried out by means of muon-spin-rotation. The absolute values of λ ab at T = 0 were found to be 189(5) nm and 195(5) nm for Sm and Nd substituted samples, respectively. The analysis of the magnetic penetration depth data within the Uemura classification scheme, which considers the correlation between the superconducting transition temperature Tc and the effective Fermi temperature TF , reveal that both families of Fe-based superconductors (with and without fluorine) falls to the same class of unconventional superconductors. One of the interesting questions, which still awaits to be explored, is to which class of the superconducting materials the newly discovered Fe-based superconductors belong. The search for relations between the various physical variables such as transition temperature, magnetic field penetration depth, electrical conductivity, energy gap, Fermi temperature etc. may help to answer this question. Among others, there is a correlation between T c and the zero-temperature inverse squared magnetic field penetration depth [λ −2 (0)], that generally relates to the zero-temperature superfluid density (ρ s ) in terms of ρ s ∝ λ −2 (0). In various families of underdoped HTS's there is the empirical relation T c ∝ ρ s ∝ λ −2 (0), first identified by Uemura et al. [6,7]. In this respect it is rather remarkable that the first magnetic field penetration measurements on LaO 1−x F x FeAs (x = 0.1, 0.075) [9] and SmO 0.82 F 0.18 FeAs [10] result in values of the superfluid density which are close to the Uemura line for hole doped cuprates, indicating that the superfluid is also very dilute in the oxypnictides.In this paper we focus on the different classification scheme proposed by Uemura [7,8] which considers the correlation between T c and the effective Fermi temperature T F determined from measurements of the in-plane magnetic penetration depth λ ab . Within this scheme strongly correlated unconventional superconductors, as HTS's, heavy fermions, Chevrel phases, or organic superconductors form a common but distinct group, characterized by a universal scaling of T c with T F such that 1/10 > T c /T F > 1/100. We show that within the Uemura classification scheme both families of oxypnictide superconductors (with and without fluorine) falls to the same class of unconventional superconductors.Details on the sample preparation for SmFeAsO 0.85 and NdFeAsO 0.85 can be found elsewhere [5]. The muonspin rotation (µSR) experiments were performed at the πM3 beam line at the Paul Scherrer Institute (Villigen, Switzerland). During the experiments we were mostly concentrated on SmFeAsO 0.85 which shows the highest T c among other oxypnictide superconductors discovered till now. For NdFeAsO 0.85 we studied only the temperature dependence of the superfluid density in a field of 0.2 T.We first start our discussion with zero-field (ZF) and lo...