Study on the growth and scintillation mechanism of Li ⁺ -doped Cs ₃ Cu ₂ I ₅ crystal with an excellent FOM value for dual gamma-ray and neutron detection applications.

Electron injection from the excited singlet state of the molecular chromophore perylene into the rutile single crystal of the wide band gap semiconductor TiO₂ was investigated with two photon photoemission (2PPE) spectroscopy in ultra-high-vacuum. The chromophore was attached to the (110) surface via acidic anchors of a tripod spacer-cum-anchor group. The corresponding wet-chemistry preparation step was performed in a special ultra-high-vacuum chamber that can accommodate solvents. Two electron injection times, i.e., 700 fs and 7 ps, were obtained with about equal weight factors from the fit to the measured time-dependent decay of the excited singlet state of the chromophore. UPS and 2PPE data showed the energetic position of the donor state at 0.5 eV above the bottom of the conduction band of rutile (110). The latter position confirmed the validity of the so-called wide band limiting case, where electron transfer is controlled only by the strength of the electronic coupling and not in addition by Franck–Condon factors. The two different injection times were attributed to two different adsorption configurations with two different distances for the chromophore from the crystal surface. A plausible configuration for the largest reaction distance suggests 1 nm distance between the rim of the chromophore and the surface atoms. The latter distance was identified with the 7 ps injection time, whereas the 10-times shorter injection time was attributed to a non-identified second adsorption configuration with an about 0.25 nm shorter reaction distance.

Study on the growth of a Li ⁺ -doped CsCu ₂ I ₃ crystal for dual gamma-ray and neutron detection.

Gd₂Si₂O₇:Ce (GPS:Ce) and (Gd,La)₂Si₂O₇:Ce (La-GPS:Ce) phosphors with different crystal structures, tetragonal, orthorhombic and triclinic, were synthesized via a sol–gel technique. The prepared samples have been systematically investigated using room temperature (RT) XRD, high temperature (HT) XRD, HRTEM, selected area electron diffraction (SAED) and EDS elemental analysis. The results show that the phase transition occurred at 1350–1450 °C and the tetragonal phase was a low-temperature metastable phase and the orthorhombic and triclinic structures were stable at high temperatures. It was observed that the three structures display completely different luminescence efficiencies under both UV lamp and X-ray excitation, but the decay time was not strongly dependent on the crystal structure. The luminescence thermo-stability and activation energy were also measured and calculated. The results indicate that the thermo-stability was strongly dependent on the crystal structure and the GPS:Ce-1500 °C sample showed the best thermo-stability. The three materials have potential application as a novel type of scintillator.

CsCu₂I₃ crystal is a promising Cu-based halide material for scintillation detection. In this paper, Na⁺ ion-doped CsCu₂I₃ crystals with a size of ϕ12 mm × 50 mm were grown successfully using the vertical Bridgman method, and the properties were systematically investigated. CsCu₂I₃:Na crystals exhibit yellow light emission peaking at 575 nm and a large Stokes shift of 1.55 eV. Based on the results of the XRD and XPS, the Na⁺ was introduced successfully. The optical absorption spectra show that the band gap of CsCu₂I₃ crystals was narrowed when the Na⁺ was doped. The photoluminescence quantum efficiency (PLQY) is improved from 16.4% to 19.6%. Finally, the X-ray-induced afterglow, and scintillation (energy resolution, light yield and decay time) under a ¹³⁷Cs source were measured and discussed. These results illustrate that CsCu₂I₃:Na crystals have potential applications in the radiation detection field.