Synthesis and Characterization of Lightweight Beryllium Chloro Silicate Phosphor

In this chapter, low weight barium-based cholorsilicate Ba5Cl6Si2O6:Eu2+ is prepared through a solid-state reaction. To confirm the structure of the synthesized phosphors, powder photographs were obtained using an x-ray diffractometer. Photoluminescence spectra and FTIR spectra were recorded. Photoluminescence spectra are studied. The emission peak is observed at 407 nm at excitation 275 nm. The intense violet-blue emission is obtained. The broad excitation band and strong emission indicate that Ba5Cl6Si2O6:Eu2+could be a good phosphor candidate for blue LED and white LEDs. Decay curve indicates the phosphor has a long afterglow feature.

Near-infrared-to-visible upconversion from 980 nm excitation band by binary solid of PbS quantum dot with direct attaching emitter

Long wavelength NIR photon upconversion (UC) by triplet-triplet annihilation in cast solid was reported. By NIR excitation at 975 nm to the binary solid of PbS quantum dot (QD) and...

Acousto-Optic Cells with Phased-Array Transducers and Their Application in Systems of Optical Information Processing

This paper presents the results of theoretical and experimental studies of anisotropic acousto-optic interaction in a spatially periodical acoustic field created by a phased-array transducer with antiphase excitation of adjacent sections. In this case, contrary to the nonsectioned transducer, light diffraction is absent when the optical beam falls on the phased-array cell at the Bragg angle. However, the diffraction takes place at some other angles (called “optimal” here), which are situated on the opposite sides to the Bragg angle. Our calculations show that the diffraction efficiency can reach 100% at these optimal angles in spite of a noticeable acousto-optic phase mismatch. This kind of acousto-optic interaction possesses a number of interesting regularities which can be useful for designing acousto-optic devices of a new type. Our experiments were performed with a paratellurite (TeO2) cell in which a shear acoustic mode was excited at a 9∘ angle to the crystal plane (001). The piezoelectric transducer had to nine antiphase sections. The efficiency of electric to acoustic power conversion was 99% at the maximum frequency response, and the ultrasound excitation band extended from 70 to 160 MHz. The experiments have confirmed basic results of the theoretical analysis.

A data-driven approach to predicting band gap, excitation, and emission energies for Eu2+-activated phosphors

An integrated ML model platform is developed to predict the peak emission wavelength (PEW), excitation band edge wavelength (EBEW), and band gap (Eg) from structural, elemental, chemical, and physical descriptors of Eu2+-activated phosphors.

Flat-band physics in the spin-1/2 sawtooth chain

We consider the strongly anisotropic spin-1/2 XXZ model on the sawtooth-chain lattice with ferromagnetic longitudinal interaction Jzz = ΔJ and aniferromagnetic transversal interaction Jxx = Jyy = J > 0. At Δ = −1∕2 the lowest one-magnon excitation band is dispersionless (flat) leading to a massively degenerate set of ground states. Interestingly, this model admits a three-coloring representation of the ground-state manifold [H.J. Changlani et al., Phys. Rev. Lett. 120, 117202 (2018)]. We characterize this ground-state manifold and elaborate the low-temperature thermodynamics of the system. We illustrate the manifestation of the flat-band physics of the anisotropic model by comparison with two isotropic flat-band Heisenberg sawtooth chains. Our analytical consideration is complemented by exact diagonalization and finite-temperature Lanczos method calculations. Graphical abstract

A luminescent Eu coordination polymer with near-visible excitation for sensing and its homologues constructed from 1,4-benzenedicarboxylate and 1H-imidazo[4,5-f][1,10]-phenanthroline

Ln-CPs were constructed to achieve luminescent Eu-CP excited at a wide excitation band including the visible region for sensing.

Synthesis, crystal structure and photoluminescence of the salts Cation+ [M(caffeine)Cl]− with Cation+=NnBu4+, AsPh4+ and M==Zn(II), Pt(II)

The salts (NnBu4)[Zn(caffeine)Cl3] and (AsPh4)[Pt(caffeine)Cl3] were prepared and their crystal structures determined by single crystal X-ray diffraction. The free ligand caffeine, as well as the complex anions [M(II)(caffeine)Cl3]− with M = Zn and Pt show an absorption spectrum with an intense band at λmax = 275 nm, which is attributed to an IL π–π* transition of the caffeine. A second band at ca. 300 nm is much weaker and largely obscured by the π–π* band. This second band is assigned to an IL n–π* transition. Both complex anions exhibit a photoluminescence (fluorescence), which originates from the n–π* state. The position of the n–π* state is recognized by the excitation band which distinctly overlaps with the fluorescence band.