The present work reports for

The present work reports for the first time the synthesis of Ca5(PO4)3Cl:Eu2+ phosphor via the Pechini (citrate gel) method and the investigation of its photoluminescent properties.
Experimental For synthesis of Eu2+ activated chlorapatite phosphor Ca5(PO4)3Cl stoichiometric amount of the precursors Ca(NO3)2 · 4H2O, Eu2O3 converted to Eu(NO3)3 · 6H2O, CaCl2 · 2H2O and (NH4)H2PO4 were taken in a china clay basins and dried in a desiccator. All the dried precursors were then finely milled and mixed together. Stoichiometric amount of Citric monohydrated and Ethylene glycol along with 2 drops of Glacial acetic acid were added to dried precursors and stirred continuously. On slow heating up to 140°C for ∼1h, the solution boils with the evolution of pale yellowish brown fumes and the process of gelation started. The mixture was then allowed to cool leading to a thick pale yellow gel. The gel was further heated slowly up to 350°C in air. The polymerization took place and a pale yellow resin/foam was formed and was pyrolysed into stunning black foam at 450°C, which started burning at 600°C. The complete pyrolysis took place at 750°C for 2h. The white powder so obtained was slowly reduced first at 600°C for 1h and then at 970°C for 3h in presence of charcoal in order to reduce the trivalent activator to divalent state. Thus white crystalline Ca5(PO4)3Cl:Eu2+ phosphor was prepared.
Results and discussion
Conclusions For the first time Eu2+ doped chlorapatite phosphor Ca5(PO4)3Cl was synthesized by novel Pechini (citrate gel) method. Photoluminescence measurements showed that Eu2+ doped chlorapatite phosphor Ca5(PO4)3Cl synthesized by this method exhibits intensive blue wide-band emission with maximum intensity at 456nm under near-UV excitation. Both blue and white LEDs can be fabricated by pre-coating the above synthesized phosphors onto 395nm-emitting InGaN chips. Moreover, the strong order AZD1152-HQPA of phosphor in the range of 300nm to 410nm makes this Eu2+-activated chlorapatite phosphor a potential candidate as a blue component (one of the three primary color components) for fabrication near-UV based phosphor converted white LEDs.
Acknowledgments
Introduction Numerous data of preclinical studies performed on various models of memory impairment indicates that agonists of sigma-1 receptors show much promise as drugs to treat cognitive dysfunction [1,2,20,61–63]. Adjusting the excitability of the neuronal plasma membrane through the sigma-1 receptor probably plays a key role in preventing neurologic diseases. Generally, it can be claimed with certainty that the sigma-1 receptor acts as an intracellular modulator:
The sigma-1 receptor has a protective function in different tissues. The effect of this receptor is mediated by regulation of cell metabolism, suggesting its involvement in various neuropsychiatric diseases [1]. These receptors regulate various ion channels, including potassium, calcium, chlorine, and NMDA-receptors, release various neurotransmitters, provide lipid transport and brain-derived neurotrophic factor (BDNF) signaling, myelination, neurito- and synaptogenesis, which shows high therapeutic potential for the sigma-1 receptor ligands. The modulating effect of sigma-1 receptors on neurotransmitter systems includes enhancing the glutamatergic, cholinergic, and serotoninergic neurotransmission. In contrast, the activation of sigma-1 receptors reduces the intensity of noradrenaline release and gamma-aminobutyric acid. An increase or a decrease of the calcium current due to the effect of sigma-1 receptors explains why the selective agonists of these receptors can modulate a wide range of neuronal effects, including a key mechanism by which sigma-1 receptors influence learning and memory processes [2].
Molecular biology of the sigma-1 receptor This receptor is a highly conserved mammalian protein [3,4]. Sequence alignment showed that the protein sequence is 30% identical (the homology is 67%) to yeast C8-C7 sterol isomerase, but the receptor itself does not exhibit this enzymatic activity [5].