The cover picture shows a microfl uidic channel and the magnetochromatic microspheres it generates. From a single-synthesis environment, structural-colored microspheres are synthesized by combining an optofl uidic approach with a magnetic property tuning method. The main image features the dynamic color tuning capability of the method; differently colored microspheres are generated in a single microfl uidic channel, and color can be changed in real-time during the synthesis process. The microspheres are produced with controlled and heterogeneous optical properties. They comprise 1D chain arrangements of magnetic nanoparticles, as shown by the microsphere in the foreground. The magnetic nanoparticles enable the microspheres to have the unique structural color. Orientation-dependent color diffraction of the magnetochromatic microspheres can be utilized to form structural color patterns using a patterned magnet. For more information, please read the Communication "Real-Time Optofl uidic Synthesis of Magnetochromatic Microspheres for Reversible Structural Color Patterning" by S. Kwon and coworkers, beginning on page 1163.The frontispiece features the multistrata nanoparticle-a single-core, fi ve-layered nanostructure. It combines tunable, dual-peak, UV-vis-NIR spectrum extinction characteristics; trimodal imaging contrast; a simple synthesis; and facile surface modifi cation capabilities into a single <60-nm-diameter, multifunctional nanosphere that seeks to relieve current methodological limitations by coupling diagnostics and therapeutics into one single theranostic tool. The image shows a model of the interior, multilayered, metallodielectric structure, including a schematic of the fabrication protocol. For more information, please read the Communication "The Multistrata

W-band pulsed EPR and ENDOR investigations of X-ray irradiated nanoparticles of synthetic hydroxyapatite Ca(9)Pb(PO(4))(6)(OH)(2) are performed. It is shown that in the investigated species lead ions probably replace the Ca(1) position in the hydroxyapatite structure.

The absorption spectra of KZnF3:Tl+ and KMgF3:Tl+ crystals have been measured over the energy range 1.5-6.4 eV at temperatures of 10-300 K. A wide absorption band with a clear doublet structure identified as an absorption A band of Tl+ impurity centres is observed for both crystals. The position of the band, its bandwidth and the distribution of absorption intensity between the two components of the band are temperature dependent in the range T>65 K. All features of the absorption spectra of the crystals studied are explained within the frameworks of the conventional theory on the basis of the Frank-Condon principle and the semiclassical picture of crystal lattice vibrations. The band shapes calculated by the Monte Carlo method are in satisfactory agreement with observed ones.

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The luminescence spectra of KZnF3:Tl+ and KMgF3:Tl+ crystals with a perovskite structure were investigated in the temperature range of 4.2–300 K and at optical excitation in the A absorption band (∼6 eV). The spectrum of KZnF3:Tl+ at 300 K is a wide band with the maximum Emax at 5.48 eV and the width of about 0.47 eV. At 100 K the band splits into two components: an intensive one with Emax = 5.63 eV and a width of about 0.2 eV and a weak one with Emax = 4.66 eV. At 4.2 K an intensive broad band practically disappears and a narrow line accompanied by a vibration structure is observed at E = 5.725 eV. This line is assigned to a zero-phonon transition from the metastable 3 Γ 1u level to the ground 1 Γ 1g level, weakly allowed due to the hyperfine interaction and phonon-assisted mechanisms. The spectrum of KMgF3:Tl+ at 300 K is a band with the maximum at 5.78 eV and a width of about 0.3 eV. This band does not disappear at 4.2 K; its maximum shifts to higher frequencies (5.91 eV) and an intensive narrow line at 5.812 eV is observed on its background. The temperature-dependent luminescence decay was also investigated. At T = 10 K the lifetime of the slow component of luminescence is τs = 11.6 ms for KZnF3:Tl+ and τs = 14.9 ms for KMgF3:Tl+. The main features of the observed luminescence spectra are satisfactorily explained within the framework of the conventional theory, as a manifestation of the Jahn–Teller effect for the excited 6sp electron configuration of an admixture Tl+ ion, with a set of model parameters close to that used earlier to describe absorption spectra of the studied crystals.