Luminescence features of Ho3+ , Er3+ and Tm3+ ions in red lead added non-conventional antimony oxide glass system.

In this study, a glass system based on heavy metal oxides, namely Pb3 O4 -Sb2 O3 -SiO2 , was prepared with Ho2 O3 , Er2 O3 , and Tm2 O3 as dopants. The prepared glass were characterized using X-ray diffraction (XRD) and infrared (IR) studies. The luminescence efficiencies of the three rare earth ions viz., Ho3+ , Er3+ , and Tm3+ in the glass system were investigated, specifically focusing on green (Ho3+ , Er3+ ), blue (Tm3+ ), and near-infrared (NIR) emissions. The optical absorption (OA) and photoluminescence (PL) spectra of RE mixed glass displayed strong bands in the visible and NIR regions, which were analyzed using the Judd-Ofelt (J-O) theory. The J-O coefficients (Ωλ ) were found to be in the order of Ω2 > Ω4 > Ω6 for all the three glass. Notably, the Tm3+ -doped glass exhibited the lowest Ω2 value, which was attributed to a larger degree of disorder in the glass network due to lower fractions of Sb5+ and Pb4+ ions that take part in the glass network forming. This conclusion was arrived based on the IR studies. Furthermore, the quantitative analysis of PL spectra and decay curves indicated that SbHo and SbEr glass were suitable for efficient green emission, while SbTm glass is a promising choice for blue laser emission.

Amplification of blue emission of Tm3+ ions in Li2 O-HfO2 -SiO2 glass system by means of Au0 metallic particles.

Li2 O-HfO2 -SiO2 -Tm2 O3 :Au2 O3 glass samples (containing fixed content of Tm2 O3 and different concentration of Au2 O3 ) were prepared and characterized. Bearing of Au0 metallic particles (MPs) on improving blue emission of thulium ions (Tm3+ ) ions was explored. Optical absorption (OA) spectra exhibited multiple bands excited from 3 H6 of Tm3+ . Additionally, a broad peak in the wavelength range 500-600 nm due to surface plasmon resonance (SPR) of Au0 MPs was noticed in the spectra. Photoluminescence (PL) spectra (of thulium free glasses) indicated a peak in the visible range due to sp → d electronic transition of Au0 MPs. Luminescence spectra of Tm3+ and Au2 O3 co-doped glasses exhibited intense blue emission with substantial increase of intensity with increase of Au2 O3 content. Bearing of Au0 MPs on the reinforcement of blue emission of Tm3+ was discussed in detail with kinetic rate equations.

Influence of nanosized defects on photoluminescence efficiency of Er3+ ions co-doped with Au2 O3 in a lead boroselenate glass ceramic system: a novel approach using positron annihilation lifetime spectroscopy.

This study consists of the results of an investigation into the influence of the free-volume space (fv ) defects on luminescence efficiency (LE) of erbium ions in Au2 O3 -doped PbO-B2 O3 -SeO2 (PBS) glass ceramics. Glass ceramics containing fixed concentrations of Er3+ ions and varied concentrations of Au2 O3 were synthesized. X-ray diffraction studies indicated that the samples contained Au2 (SeO3 )3 crystalline phase and nano gold metallic particles. The concentration of defects entrenched in the glass ceramics estimated in terms of Au2 O3 content using positron annihilation lifetime spectroscopy measurement indicated the highest content in the glass ceramic containing 0.075 mol% of Au2 O3 . Optical absorption and the photoluminescence (PL) spectra of the glass ceramics were studied in the visible region. The observed increase of PL efficiency was attributed to the enhanced concentration of free-volume imperfections in the samples. A perfect correlation could be achieved between the free-volume fraction and the PL efficiency of erbium ions in these glass ceramics.

Tetraphenylethene-Based Conjugated Fluoranthene: A Potential Fluorescent Probe for Detection of Nitroaromatic Compounds.

This study reports the synthesis and photophysical properties of a star-shaped, novel, fluoranthene-tetraphenylethene (TFPE) conjugated luminogen, which exhibits aggregation-induced blue-shifted emission (AIBSE). The bulky fluoranthene units at the periphery prevent intramolecular rotation (IMR) of phenyl rings and induces a blueshift with enhanced emission. The AIBSE phenomenon was investigated by solvatochromic and temperature-dependent emission studies. Nanoaggregates of TFPE, formed by varying the water/THF ratio, were investigated by SEM and TEM and correlated with optical properties. The TFPE conjugate was found to be a promising fluorescent probe towards the detection of nitroaromatic compounds (NACs), especially for 2,4,6-trinitrophenol (PA) with high sensitivity and a high Stern-Volmer quenching constant. The study reveals that nanoaggregates of TFPE formed at 30 and 70% water in THF showed unprecedented sensitivity with detection limits of 0.8 and 0.5 ppb, respectively. The nanoaggregates formed at water fractions of 30 and 70% exhibit high Stern-Volmer constants (Ksv=79,998 and 51,120 M(-1), respectively) towards PA. Fluorescence quenching is ascribed to photoinduced electron transfer between TFPE and NACs with a static quenching mechanism. Test strips coated with TFPE luminogen demonstrate fast and ultra-low-level detection of PA for real-time field analysis.

Visible Light Driven Metal-Free Photoredox Catalyzed α-benzylation and α-oxygenation of N-substituted Tetrahydroisoquinolines: Applications to Synthesis of Natural Products.

Herein, visible light mediated organophoto redox catalysed simple and convenient method for the α-benzylation and α-oxygenation of tertiary amines is demonstrated. Synthesis of novel thiophenol based donor acceptor organophotoredox catalysts 4 a-4 d were investigated along with commercial catalyst 4-CzIPN (4 e). A diverse biologically active α-benzylated tetrahydroisoquinolines and natural products such as (±)-Norlaudanosine, (±)-laudanosine and (±)-xylopinine have been synthesized under the optimized conditions in yields ranging from from 62-91%. Exploitation of synthesized α-benzylated compound using present phtoredox catalyzed conditions gave rise to dehydyrogenative benzylic oxidation product under oxygen atmosphere which is known to display biologically and structurally important properties. Also, various N-protected tertiary amines were found to be suitable for the α-oxygenation reactions using catalyst 4 e and resulted in good yields (61-85%).

A ladder coordination polymer based on Ca(2+) and (4,5-dicyano-1,2-phenylene)bis(phosphonic acid): crystal structure and solution-state NMR study.

The preparation of coordination polymers (CPs) based on either transition metal centres or rare-earth cations has grown considerably in recent decades. The different coordination chemistry of these metals allied to the use of a large variety of organic linkers has led to an amazing structural diversity. Most of these compounds are based on carboxylic acids or nitrogen-containing ligands. More recently, a wide range of molecules containing phosphonic acid groups have been reported. For the particular case of Ca(2+)-based CPs, some interesting functional materials have been reported. A novel one-dimensional Ca(2+)-based coordination polymer with a new organic linker, namely poly[[diaqua[µ4-(4,5-dicyano-1,2-phenylene)bis(phosphonato)][µ3-(4,5-dicyano-1,2-phenylene)bis(phosphonato)]dicalcium(II)] tetrahydrate], {[Ca2(C8H4N2O6P2)2(H2O)2]·4H2O}n, has been prepared at ambient temperature. The crystal structure features one-dimensional ladder-like ∞(1)[Ca2(H2cpp)2(H2O)2] polymers [H2cpp is (4,5-dicyano-1,2-phenylene)bis(phosphonate)], which are created by two distinct coordination modes of the anionic H2cpp(2-) cyanophosphonate organic linkers: while one molecule is only bound to Ca(2+) cations via the phosphonate groups, the other establishes an extra single connection via a cyano group. Ladders close pack with water molecules through an extensive network of strong and highly directional O-H...O and O-H...N hydrogen bonds; the observed donor-acceptor distances range from 2.499 (5) to 3.004 (6) Šand the interaction angles were found in the range 135-178°. One water molecule was found to be disordered over three distinct crystallographic positions. A detailed solution-state NMR study of the organic linker is also provided.

Crystal structure of a compact three-dimensional metal-organic framework based on Cs+ and (4,5-di-cyano-1,2-phenyl-ene)bis-(phospho-nic acid).

A new metal-organic framework compound, poly[[µ7-dihydrogen (4,5-di-cyano-1,2-phenyl-ene)diphospho-nato]-(oxonium)caesium], [Cs(C8H4N2O6P2)(H3O)] n (I), based on Cs+ and the organic linker 4,5-di-cyano-1,2-phenyl-ene)bis-(phospho-nic acid, (H4cpp), containing two distinct coordinating functional groups, has been prepared by a simple diffusion method and its crystal structure is reported. The coordination polymeric structure is based on a CsO8N2 complex unit comprising a monodentate hydro-nium cation, seven O-atom donors from two phospho-nium groups of the (H2cpp)2- ligand, and two N-atom donors from bridging cyano groups. The high level of connectivity from both the metal cation and the organic linker allow the formation of a compact and dense three-dimensional network without any crystallization solvent. Topologically (I) is a seven-connected uninodal network with an overall Schäfli symbol of {417.64}. Metal cations form an undulating inorganic layer, which is linked by strong and highly directional O-H⋯O hydrogen-bonding inter-actions. These metallic layers are, in turn, connected by the organic ligands along the [010] direction to form the overall three-dimensional framework structure.