Abnormal push-pull benzo[4,5]imidazo[1,2-a][1,2,3]triazolo[4,5-e]pyrimidine fluorophores in planarized intramolecular charge transfer (PLICT) state: Synthesis, photophysical studies and theoretical calculations

The combination of excellent luminescence with high solvent polarity effect and aggregation induced emission (AIE) is an ideal combination for creating fluorophores/probes with high microenvironmental sensitivity. However, many push-pull chromophores of the D−A type in common intramolecular charge transfer (ICT) state with a significant solvatochromic effect and AIE activity, have poor luminescent properties. Herein, to overcome this problem by using reactions of nucleophilic aromatic hydrogen substitution (SNH), we have designed a series of novel 4-heteroaryl-substituted 2-aryl-2H-benzo[4,5]imidazo[1,2-a][1,2,3]triazolo[4,5-e]pyrimidine fluorophores possessing a planarized intramolecular charge transfer (PLICT) state. All these fluorophores exhibited high luminescence quantum yields (up to 60%) and large Stokes shift values of up to 7459 cm−1. Among them, the fluorophore 4h was found to exhibit the most pronounced positive solvatochromic effect and the probe 4f exhibited the most pronounced aggregation induced emission characteristics. This AIE behavior was further confirmed by means of time-resolved fluorescence lifetime measurements as well as DFT-assisted geometry optimization studies. In the presence of trifluoroacetic acid (TFA) compound 4h exhibited a well-pronounced acidochromism via visible color change from yellow-green to orange which returned to the original yellow-green solution after the addition of triethylamine (TEA). The Stern-Volmer constant for the probe 4h towards TFA was 38 M−1. Finally, for the compounds 4f, g, h theoretical calculations in the ground and excited states in different solvents were carried out to confirm the PLICT process. Based on all above the herein reported PLICT fluorophores 4a-h can be successfully applied as biological probes and optical switches. © 202

Construction and performance of a silicon photomultiplier/extruded scintillator tail-catcher and muon-tracker

A prototype module for an International Linear Collider (ILC) detector was built, installed, and tested between 2006 and 2009 at CERN and Fermilab as part of the CALICE test beam program, in order to study the possibilities of extending energy sampling behind a hadronic calorimeter and to study the possibilities of providing muon tracking. The "tail catcher/muon tracker" (TCMT) is composed of 320 extruded scintillator strips (dimensions 1000 mm x 50 mm x 5 mm) packaged in 16 one-meter square planes interleaved between steel plates. The scintillator strips were read out with wavelength shifting fibers and silicon photomultipliers. The planes were arranged with alternating horizontal and vertical strip orientations. Data were collected for muons and pions in the energy range 6 GeV to 80 GeV. Utilizing data taken in 2006, this paper describes the design and construction of the TCMT, performance characteristics, and a beam-based evaluation of the ability of the TCMT to improve hadronic energy resolution in a prototype ILC detector. For a typical configuration of an ILC detector with a coil situated outside a calorimeter system with a thickness of 5.5 nuclear interaction lengths, a TCMT would improve relative energy resolution by 6-16 % for pions between 20 and 80 GeV.Comment: 23 pages, 18 figures, 4 tables, submitted to JINS