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Colloidal organic–inorganic lead halide perovskites have gained tremendous attention due to their excellent optical properties and promising future in optoelectronic applications. However, the lack of large scale synthesis methods and structural instability in moisture conditions restrict their practical applications. We report, for the first time, a gram-scale aqueous synthesis of MAPbBr3 (MA = CH3NH3+) using PbCO3, bottom-up synthesis of MAPbBr3 NCs and in situ bottom-up synthesis of MAPbBr3@poly(3-bromothiophene) nanocomposite. The synthesized nanocomposite material exhibits bright green fluorescence and excellent water-resistivity. Together, the polymer-based bottom-up and in situ encapsulation strategy of MAPbBr3 NCs will pave the way for synthesizing other lead halide water-resistant perovskites that will be used in thin-film based light-emitting devices. [ABSTRACT FROM AUTHOR]

Proper fusion of fluorescence mechanisms in a single fluorophore unit is highly desirable to obtain better sensitivity, as well as selectivity towards a particular metal ion. In this regard, a Zn2+ chemosensor exhibiting strong fluorescence through synergistic CHEF-PET-ESIPT fluorescence mechanism has not received substantial deployment. This type of chemosensor provides an ample avenue to detect metal ions with a large stokes shift and are useful in living cell imaging study. Herein, we report an unparalleled Zn2+ chemosensor (L) based on these three types of fluorescence mechanisms by condensing 2,6-diformyl-4-methylphenol and 2-hydrazinyl-4,6-dimethylpyrimidine. All the three types of mechanism were experimentally verified by UV-Vis, fluorescence and time resolved photoluminescence (TRPL) spectroscopic evaluation. The sensor L and Zn2+ formed a 1 : 1 ratio complex demonstrating a high binding constant value (Ka = 4.812 × 105 M−1) and L showed clear discrimination from the Cd2+ ion. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 9.727 × 10−7 (M) and 3.24 × 10−6 (M), respectively. We have also shown that cell imaging can be performed using L without many cytotoxicity concerns. [ABSTRACT FROM AUTHOR]

5-methoxy isatin-appended rhodamine dye, (E)-3'-(diethylamino)-6'-(ethyl(methyl)amino)-2-((5-methoxy-2-oxoindolin-3-ylidene)amino)spiro[isoindoline-1,9'-xanthen]-3-one (L) has been designed, synthesized, and characterized by different spectroscopic techniques. The chemosensor L shows high sensitivity towards Al3+ ions without interference from other biologically important cations in DMSO/H2O (1/9, v/v) media. The Al3+-ion promoted ring opening of the rhodamine spirolactam ring in chemosensor L evokes a fluorescence turn-on response via chelation-enhanced fluorescence (CHEF) process. Its lowest detection limit for Al3+ is 2.2x10-8 M, and displays a significant color change from almost colorless to deep pink in the presence of Al3+. The titration results show a 1:1 complex formation between chemosensor L and Al3+. [ABSTRACT FROM AUTHOR]

A novel fluorescent chemosensor based on a rhodamine derivative (L) was designed, synthesized, and used as a selective Al+3 ion sensor. Upon addition of Al3+ to an aqueous-acetonitrile solution of L, the development of a strong fluorescence signal by a chelation-enhanced fluorescence (CHEF) process was observed with an attractive glowing orange emission. This sensor shows high selectivity towards Al3+ ions in the presence of other competing metal ions. The fluorescence quantum yield of L–Al3+ (Φf = 0.30) was found to be very high compared to the bare ligand. The limit of detection (LOD) of Al3+ ions was calculated to be 2 × 10−8 M by fluorescence titration. The 1 : 1 binding stoichiometry of the metal complex was established by combined UV-vis, fluorescence and TOF-MS spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: A novel rhodamine-based chemosensor, 3′,6′-bis(diethylamino)-2-((2,7-dimethoxy-9H-fluoren-9-ylidene)amino)spiro[isoindoline-1,9′-xanthen]-3-one (1) for aluminum ion, was designed and synthesized. Compound 1 is an orange colored, weak fluorescent compound which was synthesized via one-step facile reaction of rhodamine B hydrazide with 2,7-dimethoxy-9H-fluoren-9-one in MeOH. When Al3+ salt was added in methanol:water (30:70, v/v) solution then spirolactum ring of 1 was opened. The absorbance and fluorescence of the mixed solution were increased dramatically because of the opening of the lactum ring. Thus, signal transduction occurred via reversible CHEF (chelation-enhanced fluorescence) mechanism in the range 580–584nm. [Copyright &y& Elsevier]

Abstract: One new dinuclear Zn(II) complex, [(N3)Zn(L1)(μ1,1-N3)]2 (1), and a dinuclear Cd(II) complex, [(N3)Cd(L1)(μ1,1-N3)]2 (2), of the potentially tridentate NNN-donor Schiff base ligand N-(4,6-dimethyl-pyrimidin-2-yl)-N′-(1-pyridin-2-yl-ethylidine)-hydrazine (L1) and another dinuclear Cd(II) complex [(NCS)Cd(L2)(μ1,3-NCS)]2 (3) of a similar NNN donor Schiff base ligand, N-(4,6-dimethyl-pyrimidin-2-yl)-N′-pyridin-2-ylmethylene-hydrazine (L2), have been synthesized and characterized by elemental analyses, IR, 1H NMR, fluorescence spectroscopy and single crystal X-ray crystallography. The fluorescence spectral changes observed upon addition of the Zn(II) ion to a mixture of L1 and azide showed high selectivity towards the Zn(II) ion over other metal ions. The ligands L1 and L2 are [1+1] condensation products of 2-hydrazino-4,6-dimethyl pyrimidine with 2-acetyl pyridine and pyridine-2-carbaldehyde, respectively. In the complexes 1 and 2 the two Zn(II) and Cd(II) centers are held together by μ1,1-bridged azide ions, while in 3 the two Cd(II) centers are bridged by μ1,3-thiocyanate ions. Complex 1 shows high chelation enhanced fluorescence compared to 2 and 3. All the metal centers have a distorted octahedral geometry. [Copyright &y& Elsevier]

Abstract: Two coumarin derived dyes (compounds La and L) have been synthesized in high yields by Schiff base condensation. On probing with a femtosecond laser, none of these compounds show any two-photon activity in the wavelength range, 760–860nm. However, La in presence of Zn(II) and L in presence of Mg(II), exhibit large two-photon absorption as well as emission in the same wavelength range. Theoretical calculations at the B3LYP functional with 6-31G∗ and LanL2DZ mixed basis set under DFT formalism support experimental results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Smart material synthesis through polymer encapsulated perovskite crystals. • The materials are used for Memory Recovery application. • The role of a conducting polymer in offering better emission quality and stability of the perovskite crystals. • Impressive optical properties of polymer-perovskite composite make the material for optoelectronic devices. Impressive optical properties of organic–inorganic lead halide perovskite crystals make them suitable for optoelectronic devices. However, these crystals are unstable in water and other polar solvents and quickly lose their fluorescence which cannot be recovered by the addition of non-polar solvents. Fluorescence recovery is absolute necessity for long-term stability of perovskite in optoelectronic devices. Till date, there is no report showing mechanism of fluorescence recovery of organic–inorganic lead halide perovskite crystals. Here, we have reported the synthesis of FAPbBr 3 /polypyrrole (PPy) composites (FA = Formamidinium) for shedding light on the mechanism of fluorescence recovery in presence of N,N Dimethyl formamide or DMF. We have synthesized FAPbBr 3 crystals at room temperature and tuned their band gap from green to blue by varying the amount of surfactant. Similar study was repeated with FAPbBr 3 /PPy composites, synthesized through in situ polymerization. Encapsulation was found to improve the emission quality and purity of the colour and successfully restored the fluorescence memory which was lost in presence of DMF. The recovery was attributed to resurfacing of PPy in presence of toluene which brought the building blocks of FAPbBr 3 crystals back to the co-crystallization domain. In brief, this fundamental finding could pave the future way for achieving long-term stability of perovskite crystals in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Fluorescence properties of the formed benzimidazoles in different solvents and at different pH are investigated. [ABSTRACT FROM AUTHOR]