Photoluminescent Compounds Research Articles

A Lanthanide-Based Supramolecular Nanotube and Its Photochemistry

Lanthanide complex including Europium ion (Eu3+) is one of the fascinating photoluminescent compound. However, most of lanthanide complexes are used as a mononuclear-based material without void space. Here, we developed lanthanide-based assemblies including a supramolecular nanotube. Their photophysical properties related to dynamic exciton was investigated.

Copper Iodide Clusters Coordinated by Emissive Cyanobiphenyl-Based Ligands.

Copper(I) halides are currently the subject of intensive research because of their rich photophysical properties combined with economic and eco-friendly advantages for practical applications. The molecular copper iodide cluster of the general formula [Cu4I4L4] (L = ligand) is a well-known photoluminescent compound, and the possibility to enlarge the panel of its photophysical properties is studied here, by exploring ligands bearing a distinct emitter. The comparative study of five copper iodide clusters coordinated by different phosphine ligands functionalized by the emissive cyanobiphenyl (CBP) group is thus described in this work. The emissive properties of the ligands have a great impact onto the photophysical properties of the cluster. Compared with classical [Cu4I4L4] copper iodide clusters, the origin of the emission bands is largely modified. The CBP moiety of electron acceptor character significantly lowers in energy the vacant orbitals and consequently affects the global energetic layout. These clusters present dual emission based on two different emissive centers which interplay through energy transfer. This study demonstrates that the design of original ligands is an effective approach to enrich the photophysical properties of the appealing family of copper halide complexes.

Photoluminescence with an unusual open-loop and rigid delocalized conjugated structure in quantum dots

It is well known that almost all photoluminescent molecules are aromatic or heterocyclic ring compounds for bioimaging analysis. A question remains as to whether a breakthrough can be achieved regarding a novel photoluminescent molecule without a ring structure, and in a what manner. In this study, we explored the photoelectric conversion and structure of photoluminescent compounds, and constructed an intra-molecular coupling positive–negative-junction (PNJ) with an open-loop and rigid Π56 delocalized conjugated structure of the coupling p-π conjugate system. This was performed to enable strong absorption of the R/tail-end band for the high probability of an n → π*/n → σ* electron transition for photoluminescence production. Subsequently, the Π56 structure was formed in a short-chain aliphatic molecule as a hydrolytic product of citric acid and urea, and computational methodology was employed to estimate the feasibility of the molecule photoluminescence. Finally, a quantum dot material was fabricated from the aliphatic molecule, the optical properties of the quantum dots were investigated, and the biocompatibility and bioimaging ability of quantum dots were assessed. This work presents not only a theoretical exploration but also practical application of a new strategy to obtain molecules, compounds, and materials with bioimaging.

Synthesis and characterization of luminescence of (Li-Ca-Eu)P for blue phosphor

From last few decades, phosphate dependent phosphorus and other compositional materials have gained further research interest in solid state lighting applications. Phosphate based phosphors with high photo luminescent compounds (Li,Ca, and Eu) has been synthesised using the sol gel process. Eu+2 ions play a essential character in blue emitting phosphors that are stimulated at near-UV LEDs, due to the 5d to 4f Eu2 + transformation, the Li (Ca1−x Eux)PO4 has been shown to be an effective host in the lamp industry.

Two viologen-based photoluminescent compounds: excitation-wavelength-dependent and photoirradiation-time-dependent photoluminescent switches

We synthesized two isostructural multi-coloured photoluminescent coordination polymers. They exhibit excitation-wavelength-dependent photoluminescence emission and photoirradiation-time-dependent photoluminescence emission in solid-state.

Photoluminescent and Chromic Nanomaterials for Anticounterfeiting Technologies: Recent Advances and Future Challenges.

Counterfeiting and inverse engineering of security and confidential documents, such as banknotes, passports, national cards, certificates, and valuable products, has significantly been increased, which is a major challenge for governments, companies, and customers. From recent global reports published in 2017, the counterfeiting market was evaluated to be $107.26 billion in 2016 and forecasted to reach $206.57 billion by 2021 at a compound annual growth rate of 14.0%. Development of anticounterfeiting and authentication technologies with multilevel securities is a powerful solution to overcome this challenge. Stimuli-chromic (photochromic, hydrochromic, and thermochromic) and photoluminescent (fluorescent and phosphorescent) compounds are the most significant and applicable materials for development of complex anticounterfeiting inks with a high-security level and fast authentication. Highly efficient anticounterfeiting and authentication technologies have been developed to reach high security and efficiency. Applicable materials for anticounterfeiting applications are generally based on photochromic and photoluminescent compounds, for which hydrochromic and thermochromic materials have extensively been used in recent decades. A wide range of materials, such as organic and inorganic metal complexes, polymer nanoparticles, quantum dots, polymer dots, carbon dots, upconverting nanoparticles, and supramolecular structures, could display all of these phenomena depending on their physical and chemical characteristics. The polymeric anticounterfeiting inks have recently received significant attention because of their high stability for printing on confidential documents. In addition, the printing technologies including hand-writing, stamping, inkjet printing, screen printing, and anticounterfeiting labels are discussed for introduction of the most efficient methods for application of different anticounterfeiting inks. This review would help scientists to design and develop the most applicable encryption, authentication, and anticounterfeiting technologies with high security, fast detection, and potential applications in security marking and information encryption on various substrates.

Two Novel π -Conjugated Fluorophores for Dye-Doped LC On-Off Photoluminescence Switching

Among various classes of Photoluminescent (PL) compounds, soft-matter based materials in which chromophores are embedded in a Liquid-Crystal (LC) host polymer prove to be very attractive in the production of flexible panels and on-off temperature switches. Actually, the obtainment of low cost, easily synthesizable, and stable organic molecules soluble in the LC matrix is a challenge for both scholars and technologists. Here we describe the synthesis of two new emissive dyes based on a dicyanophenylenevinylene and on a bis-azobenzene core whose PL properties were investigated as neat solids, in solution, and in particular in a dye-doped LC nematic polymer often employed in PDLC applications. 1H NMR and 13C NMR spectroscopy allow the characterization of all compounds Their thermotropic liquid- crystalline (LC) properties were examined by differential scanning calorimetry and polarizing optical microscopy. Photoluminescence properties were characterized by fluorescence spectra.

Multicolor Organometallic Mechanophores for Polymer Imaging Driven by Exciplex Level Interactions.

Photoluminescent compounds can undergo various structural changes upon interaction with light. When these changes manifest themselves in the excited state, the resulting emitters can obtain a sensory function. In this work, we designed coordination compounds that can vary their emission color in response to thermal and mechanical stimuli. When embedded in a polymer matrix, Cu–NHC sensors act as mechanophores, and their color-based response can readily describe mechanical stress and phase transition phenomena. A strong practical advantage of new mechanophores over previous generations of organometallic stress sensors stems from their reliance on emission color variations that are easy to detect. In a broad context, our work implies that emission color variations that we often view as thermally governed can also be triggered mechanically and used to generate sensory information.

Comparative Synthesis and Cyclization of 1, 5-Diketone

Diketones are found to be extremely reactive due to owing electron deficient carbon atoms of double carbonyls groups and are extensively used for huge range of organic synthesis such as tetracyclones, triazines, inidazoles, quinoxalines, pyrazinones, peroxides, Photoluminescent compounds, cis-jasmone, furan, pyrroles and thiophenes etc. 1, 5-diketone (1, 3, 5-triphenyl-1, 5-pentanedione) has been synthesized by the condensation of acetophenone and benzaldehyde at different reaction conditions while stirring at 25°C. Further, the synthesized 1, 3, 5-triphenyl-1, 5-pentanedione has been condensed with benzil and also cyclized in acidic as well as in basic media to get the product. The progress of reaction was monitored by TLC (thin layer chromatography , Eluent; n-hexane/ethylacetate) visualizing under UV lamp and Iodine bath.

Study and Development of a Fluorescence Based Sensor System for Monitoring Oxygen in Wine Production: The WOW Project

The importance of oxygen in the winemaking process is widely known, as it affects the chemical aspects and therefore the organoleptic characteristics of the final product. Hence, it is evident the usefulness of a continuous and real-time measurements of the levels of oxygen in the various stages of the winemaking process, both for monitoring and for control. The WOW project (Deployment of WSAN technology for monitoring Oxygen in Wine products) has focused on the design and the development of an innovative device for monitoring the oxygen levels in wine. This system is based on the use of an optical fiber to measure the luminescent lifetime variation of a reference metal/porphyrin complex, which decays in presence of oxygen. The developed technology results in a high sensitivity and low cost sensor head that can be employed for measuring the dissolved oxygen levels at several points inside a wine fermentation or aging tank. This system can be complemented with dynamic modeling techniques to provide predictive behavior of the nutrient evolution in space and time given few sampled measuring points, for both process monitoring and control purposes. The experimental validation of the technology has been first performed in a controlled laboratory setup to attain calibration and study sensitivity with respect to different photo-luminescent compounds and alcoholic or non-alcoholic solutions, and then in an actual case study during a measurement campaign at a renown Italian winery.

Triphenylbenzene Sensor for Selective Detection of Picric Acid.

A C 3-symmetric triphenylbenzene based photoluminescent compound, 1,3,5-tris(4'-(N-methylamino)phenyl) benzene ([NHMe]3TAPB), has been synthesized by mono-N-methylation of 1,3,5-tris(4'-aminophenyl) benzene (TAPB) and structurally characterized. [NHMe]3TAPB acts as a selective fluorescent sensor for picric acid (PA) with a detection limit as low as 2.25 ppm at a signal to noise ratio of 3. Other related analytes (i.e. TNT, DNT and DNB) show very little effect on the fluorescence intensity of [NHMe]3TAPB. The selectivity is triggered by proton transfer from picric acid to the fluorophore and ground-state complex formation between the protonated fluorophore and picrate anion through hydrogen bonding interactions. The fluorescence lifetime measurements reveal static nature of fluorescence quenching.

The photoluminescence of a fluorescent lamp: didactic experiments on the exponential decay

The lifetimes of the photoluminescent compounds contained in the coating of fluorescent compact lamps are usually measured using specialised instruments, including pulsed lasers and/or spectrofluorometers. Here we discuss how some low cost apparatuses, based on the use of either sensors for the educational lab or commercial digital photo cameras, can be employed to the same aim. The experiments do not require that luminescent phosphors are hazardously extracted from the compact fluorescent lamp, that also contains mercury. We obtain lifetime measurements for specific fluorescent elements of the bulb coating, in good agreement with the known values. We also address the physical mechanisms on which fluorescence lamps are based in a simplified way, suitable for undergraduate students; and we discuss in detail the physics of the lamp switch-off by analysing the time dependent spectrum, measured through a commercial fiber-optic spectrometer.Since the experiment is not hazardous in any way, requires a simple setup up with instruments which are commonly found in educational labs, and focuses on the typical features of the exponential decay, it is suitable for being performed in the undergraduate laboratory.

Synthesis and characterization of Li2TiSiO5 obtained by melting and solid-state reaction

In this work, the synthesis of the Li2TiSiO5 photoluminescent compound, obtained from a stoichiometric mixture of Li2CO3, SiO2 and TiO2 nanoparticles, was investigated by two different routes named route I (melting and quenching) and route II (solid-state reaction). In the route I, the raw materials were melted (1550 °C/2 h) and cooled into water. Subsequently, the solidified product was milled (30 min) in a high-energy mill. In the route II, the raw materials were directly milled (10 min). The obtained powders, from both routes, were heat treated at different temperatures (900–1000 °C/60 min) and then subjected to crystallographic (XRD) and thermal (DSC) analyses in order to investigate the resulting structure and the associated physical–chemical reactions. The results showed that it is possible to obtain the Li2TiSiO5 compound from both synthesis routes but, apparently, the route I seems to be more appropriated to obtain the Li2TiSiO5 compound and to demonstrate the photoluminescence phenomena with and even without thermal treatment.

XANES and micro-Raman spectroscopy study of the barium titanosilicates BaTiSi2O7 and BaTiSi4O11

The coordination environment around Ti4+ in the photoluminescent compound BaTiSi2O7 and in BaTiSi4O11 was investigated with X-ray absorption near-edge structure spectroscopy and micro-Raman spectroscopy. The presence of VTi in TiO5 pyramidal units with one short Ti–O bond involving the apical oxygen was detected in both compounds. Interpretation of the vibrational signal from the silicate framework suggested that BaTiSi4O11 is a metasilicate containing building units of SiO4 tetrahedra, which are larger than in other barium titanosilicates. These results confirmed the same structural environment of Ti4+ as recently disclosed by structure refinement of BaTiSi2O7 and provided new insights into the unknown structure of BaTiSi4O11 in the light of the study of its physical properties as potential functional material.

Synthesis of Octafluorobiphenyl-4,4′-dicarboxylic acid and photoluminescent compounds based thereon

Octafluorobiphenyl-4,4′-dicarboxylic acid (H2L) and its complexes with Tb(III) and Eu(III) [Ln2(H2O)4(L)3·3H2O and Ln2(phen)2(L)3·2H2O] have been prepared; their structure has been elucidated from IR spectroscopy and X-ray diffraction analysis data. Thermal properties of the compounds have been studied. The complexes of Tb(III) and Eu(III) exhibit green and red photoluminescence, respectively.

Synthesis, characterization and explosive detection of photoluminescent compounds with intramolecular charge-transfer characteristic

Synthesis, characterization and explosive detection of compounds based on 1,4(benzo-{2,1′-3})-thiadiazole, carbazole, and tetraphenylethene derivatives with intramolecular charge-transfer characteristic were illustrated in detail. The photoluminescent variations of compounds in different solvents were studied, and emission light with different wavelength ranging from yellow, green to blue can be easily obtained by just changing the solvent without tedious synthetic modification. Furthermore, the titration experiments were used to detect explosive compound of picric acid, and then calculate the detection limit of the explosive by plotting curves of two compounds with aggregation–induced emission properties in tetrahydrofuran and tetrahydrofuran/water mixture solution of 90% water. The Stern–Volmer plots of carbazole and tetraphenylethene substituted 1,4(benzo-{2,1′-3})-thiadiazole in tetrahydrofuran and tetrahydrofuran/water mixture are linear in some concentration range and give quenching constants of 1.8×107M−1 and 10.7×107M−1, respectively, and the corresponding detect ion limits as low as 0.54μg/mL and 0.13μg/mL were realized. The detect ion performance of carbazole and tetraphenylethene substituted 1,4(benzo-{2,1′-3})-thiadiazole is much better than that of tetraphenylethene substituted 1,4(benzo-{2,1′-3})-thiadiazole, which can be attributed to the relatively higher dipole moment of the corresponding compound.

Synthesis and luminescence modulation of pyrazine-based gold(III) pincer complexes.

The first examples of pyrazine-based gold(III) pincer complexes are reported; their intense photoemissions can be modified by protonation, N-alkylation or metal ions, without the need for altering the ligand framework. Emissions shift from red (77 K) to blue (298 K) due to thermally activated delayed fluorescence (TADF).

Preparation of photoluminescent compounds of Eu(III), Sm(III), and Dy(III) containing anions of tetrafluoroterephthalic acid

The Ln2(H2O)4(L)3·2H2O and Ln2(phen)2(L)3·2H2O complexes [Ln = Eu(III), Sm(III), or Dy(III); H2L = C6F4(COOH)2, phen = 1,10-phenanthroline] have been prepared. Structures of the prepared compounds have been confirmed by X-ray diffraction and IR spectroscopy studies. The complexes of Eu(III) have exhibited red photoluminescence stronger than that of the complexes of Sm(III) and Dy(III).

Structural reinvestigation of the photoluminescent complex [NdCl2(H2O)6]Cl

The structure of the photoluminescent compound hexaaquadichloridoneodymium(III) chloride has been redetermined from single-crystal X-ray diffraction data at 100 K, with the aim of providing an accurate structural model for the bulk crystalline material. The crystal structure may be described as a network of [NdCl2(H2O)6](+) cations with distorted square-antiprism geometry around the Nd(III) centre. The Nd(III) cation and the nonbonded Cl(-) anion are both located on twofold symmetry axes. The crystal packing consists of three different neodymium pairs linked by a three-dimensional network of O-H···Cl intermolecular interactions. The pair distribution function (PDF) calculated from the experimentally determined structure is used for the discussion of the local structure.

ChemInform Abstract: 2,1,3‐Benzothiadiazole and Derivatives: Synthesis, Properties, Reactions, and Applications in Light Technology of Small Molecules.

AbstractReview: 333refs.